Circulation and Respiration

Circulation and Respiration
Chapter 23 Circulation and Respiration

Biology and Society: The ABCs of Saving Lives
The transport of gases into and out of the body relies upon a close relationship between the: Circulatory system Respiratory system © 2010 Pearson Education, Inc.

Figure 23.00 Figure 23.0 Saving a life

In emergency situations, rescuers follow a set of procedures known as the ABCs of lifesaving:
A is for airway B is for breathing C is for circulation

UNIFYING CONCEPTS OF ANIMAL CIRCULATION
Every organism must exchange materials with its environment, relying upon: Diffusion, the spontaneous movement of molecules from an area of higher concentration to an area of lower concentration A circulatory system, for all but the simplest animals Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

Open and Closed Circulatory Systems
Circulatory systems consist of a: Central pump Vascular system Circulating fluid Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

(b) Closed circulatory system
O2-rich blood O2-poor blood Interstitial fluid Gill capillaries Capillary bed Heart Capillary beds Arteriole Artery (O2-rich blood) Venule Vein Atrium Heart Gill capillaries Ventricle Artery (O2-poor blood) (b) Closed circulatory system Figure 23.1b Figure 23.1b Closed circulatory system

In a closed circulatory system, blood is:
Confined to vessels Distinct from the interstitial fluid, the fluid that fills the spaces around cells Closed circulatory systems are found in: Many invertebrates, including earthworms and octopuses Vertebrates Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

The cardiovascular system of vertebrates consists of the:
Heart Blood vessels Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

In the heart the: Atrium receives blood
Ventricle pumps blood away from the heart Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

Blood is confined to three main types of blood vessels:
Arteries carry blood away from the heart Capillaries are the site of exchange between blood and interstitial fluid Veins return blood back to the heart Student Misconceptions and Concerns 1. Students might need to be reminded about the changes in surface to volume ratios as organisms increase in size. As any organism gets larger, the demand for a circulatory system coupled with a respiratory system increases, because the surface area is unable to keep up with the growing volume. 2. Students might not realize that closed circulatory systems are capable of greater pressures, when fluids remain confined to limited spaces. Teaching Tips 1. The following analogy about a home might help students distinguish between open and closed circulatory systems. Airflow through a home with a blower furnace is an open system, in which the furnace blower propels air through ducts that open into rooms. Air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system, in which water, under high pressure, is contained in pipes. The analogy is not perfect, because in part, water pipes eventually open up into sinks and toilets, before draining into the sewage system. 2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries and large animals have deep regions that are not near a surface or edge. Therefore, large countries such as the United States, Canada, and Mexico require an internal system of roads and railways to move the many goods from seaports (the edges/surfaces) to regions deep within the countries. These roads and railways work in partnership with ports in the same way that blood vessels (and blood) cooperate with a respiratory surface. 3. There are many simple demonstrations of diffusion. If you use an overhead projector, or have another bright lamp available, add a single drop of food coloring into a beaker of water placed near the light source. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.

THE HUMAN CARDIOVASCULAR SYSTEM
In the human cardiovascular system, the: Central pump is the heart Vascular system is the blood vessels Circulating fluid is the blood Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

The Path of Blood Humans and other terrestrial vertebrates have a double circulation system. A double circulation system consists of a: Pulmonary circuit between the heart and lungs Systemic circuit between the heart and the rest of the body Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

CO2 O2 CO2 CO2 Lung Lung O2 O2 Heart O2-rich blood O2 O2-poor blood
(a) Pulmonary circuit (b) Systemic circuit Figure 23.2 Figure 23.2 Double circulation

CO2 CO2 Lung Lung O2 O2 Heart O2-rich blood O2-poor blood
(a) Pulmonary circuit Figure 23.2a Figure 23.2a Double circulation: pulmonary circuit

CO2 O2 O2 O2-rich blood O2-poor blood CO2 (b) Systemic circuit
Figure 23.2b Figure 23.2b Double circulation: systemic circuit

Animation: Path of Blood in Mammals
One complete trip through the human cardiovascular system: Takes about one minute Requires two passes through the heart Animation: Path of Blood in Mammals Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Capillaries of head, chest, and arms Superior vena cava Pulmonary
artery Pulmonary artery Aorta Capillaries of lung Capillaries of lung Pulmonary vein Pulmonary vein Right atrium Left atrium Right ventricle Left ventricle Inferior vena cava Capillaries of abdominal region and legs O2-rich blood O2-poor blood Figure Figure 23.3 A trip through the human cardiovascular system (Step 11)

How the Heart Works The human heart:
Is a muscular organ about the size of a fist Is located under the breastbone Has four chambers Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Blast Animation: Anatomy of the Heart
The path of blood flow through the human heart functions as two pumps moving blood between the: Heart and lungs Heart and the rest of the body Blast Animation: Anatomy of the Heart Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

To body O2-rich blood From body O2-poor blood Right lung Left lung
Right atrium Left atrium Valves Valves Right ventricle Left ventricle From body Figure 23.4 Figure 23.4 Path of blood flow through the human heart

Blast Animation: Cardiac Cycle Overview
The Cardiac Cycle The heart relaxes and contracts throughout our lives. Diastole is the relaxation phase of the heart cycle. Systole is the contraction phase. Blast Animation: Cardiac Cycle Overview Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Figure 23.5-3 Atria contract. Blood is forced into ventricles.
Heart is relaxed. Blood flows in. 0.1 sec Diastole 0.8 sec 0.3 sec Systole 0.4 sec Ventricles contract. Blood is pumped out. Figure Figure 23.5 The cardiac cycle (Step 3)

The Pacemaker and the Control of Heart Rate
The pacemaker, or SA (sinoatrial) node: Sets the tempo of the heartbeat Is composed of specialized muscle tissue in the wall of the right atrium Blast Animation: Electrical Coordination of the Cardiac Cycle Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Figure 23.6 Wire leading to SA node Heart Artificial pacemaker
AV node Right atrium Right ventricle Pacemaker generates electrical impulses. Impulses spread through atria. Impulses reach ventricles. (a) The heart’s natural pacemaker (b) Artificial pacemaker Figure 23.6 Figure 23.6 Pacemakers

The remedy for this failure of the electrical control of the heart is:
In certain kinds of heart disease, the heart fails to maintain a normal rhythm. The remedy for this failure of the electrical control of the heart is: An artificial pacemaker, a small electronic device surgically implanted near the SA node Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Blood Vessels If the heart is the body’s “pump,” then the “plumbing” is the system of arteries, veins, and capillaries. Arteries carry blood away from the heart. Veins carry blood toward the heart. Capillaries allow for exchange between the bloodstream and tissue cells. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

All blood vessels are lined by a thin layer of tightly packed epithelial cells.
Structural differences in the walls of the different kinds of blood vessels correlate with their different functions. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

From heart To heart Epithelium Valve Epithelium Epithelium Smooth
muscle Smooth muscle Connective tissue Connective tissue Artery Vein Arteriole Venule Capillary Figure 23.8 Figure 23.8 The structure of blood vessels

Blood Flow through Arteries
The force that blood exerts against the walls of blood vessels is blood pressure. Blood pressure is the main force driving the blood from the heart to the capillary beds. A pulse is the rhythmic stretching of the arteries caused by the pressure of blood forced into the arteries during systole. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

High blood pressure, or hypertension, is:
Optimal blood pressure for adults is below 120 systolic and below 80 diastolic. High blood pressure, or hypertension, is: Persistent systolic blood pressure higher than 140 and/or Diastolic blood pressure higher than 90 Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Blood Flow through Capillary Beds
At any given time, only about 5–10% of the capillaries have a steady flow of blood. The regulation of blood flow through capillaries Is controlled by muscles Reflects shifting demands by organs of the body Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Figure 23.9 Capillary Tissue cell Red blood cell Diffusion of
O2 and nutrients out of capillary and into tissue cells Diffusion of CO2 and wastes out of tissue cells and into capillary From artery To vein Interstitial fluid LM To vein (a) Capillaries (b) Chemical exchange Figure 23.9 Figure 23.9 Chemical exchange between the blood and tissue cells

The walls of capillaries are thin and leaky.
At the arterial end of the capillary, blood pressure pushes fluid rich in oxygen, nutrients, and other substances into the interstitial fluid. At the venous end of the capillary CO2 and other wastes diffuse from tissue cells into the capillary bloodstream. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Blood Return through Veins
Blood returns to the heart: After chemicals are exchanged between the blood and body cells At a pressure that has nearly dropped to zero Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Blood moves back towards the heart because of:
Surrounding skeletal muscles that compress the veins One-way valves that permit blood flow only toward the heart Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

To heart Valve (open) Skeletal muscle Valve (closed) Figure 23.10
Figure Blood flow in a vein

Blood An adult human has about 5 L (11 pints) of blood.
By volume, blood is about: 45% cells and 55% plasma, consisting of about: 90% water 10% dissolved salts, proteins, and other molecules Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Figure 23.11 Plasma (55%) Cellular elements (45%) Red blood cells
(erythrocytes) Water (90% of plasma) Proteins Blood Dissolved salts (such as sodium, potassium, calcium) White blood cells (leukocytes) Substances being transported (such as O2, CO2, nutrients, wastes, hormones) Platelets Figure 23.11 Figure The composition of human blood

Red Blood Cells and Oxygen Transport
Red blood cells (erythrocytes) are: Shaped like discs with indentations in the middle The most numerous type of blood cell Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

CELLULAR COMPONENTS OF BLOOD
Red Blood Cells (cells that carry oxygen) White Blood Cells (cells that fight infection) Platelets (bits of membrane-enclosed cytoplasm that aid clotting) Colorized SEM Fibrin Colorized SEM Colorized SEM Colorized SEM Red blood cell Figure 23.12 Figure The three cellular components of blood

Carbohydrate-containing molecules on the surface of red blood cells determine the blood type.
Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Figure 9.20 Blood Group (Phenotype) Antibodies Present in Blood
Reactions When Blood from Groups Below Is Mixed with Antibodies from Groups at Left Genotypes Red Blood Cells O A B AB Carbohydrate A IAIA or IAi A Anti-B Carbohydrate B IBIB or IBi B Anti-A AB IAIB — Anti-A Anti-B O ii Figure 9.20 Figure 9.20 Multiple alleles for the ABO blood groups.

Each red blood cell contains large amounts of the protein hemoglobin, which:
Contains iron Transports oxygen throughout the body Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Anemia may result from:
An abnormally low amount of hemoglobin or A low number of red blood cells The hormone EPO boosts production of red blood cells. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

White Blood Cells and Defense
White blood cells (leukocytes) fight: Infections Cancer There are about 700 times more red blood cells than white blood cells. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

(cells that fight infection)
White Blood Cells (cells that fight infection) Colorized SEM Figure 23.12b Figure 23.12b The three cellular components of blood: white blood cells

Platelets and Blood Clotting
Blood contains two components that aid in clotting: Platelets, bits of cytoplasm pinched off from larger cells in the bone marrow Clotting factors released from platelets that convert fibrinogen, a protein found in plasma, into a threadlike protein called fibrin Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Stem Cells and the Treatment of Leukemia
Is cancer of white blood cells May require treatment using: Radiation Chemotherapy, and/or Bone marrow transplantation Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

(bits of membrane-enclosed cytoplasm that aid clotting)
Platelets (bits of membrane-enclosed cytoplasm that aid clotting) Colorized SEM Fibrin Colorized SEM Red blood cell Figure 23.12c Figure 23.12c The three cellular components of blood: platelets

Cardiovascular Disease
The cardiovascular system contributes to homeostasis by: Exchanging nutrients and wastes with the interstitial fluid Controlling the composition of blood by moving it through the lungs, liver, and kidneys Helping to regulate temperature by moving blood to or away from the skin Distributing hormones Defending against foreign invaders © 2010 Pearson Education, Inc. Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Cardiovascular disease:
Includes all diseases affecting the heart and blood vessels Accounts for 40% of all deaths in the United States Kills more than 1 million people each year Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Coronary arteries: Supply the heart muscle
Can narrow or close, contributing to a heart attack Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Aorta Coronary artery (supplies oxygen to the heart muscle)
Dead muscle tissue Blockage Figure 23.13 Figure Blockage of a coronary artery, resulting in a heart attack

Atherosclerosis: Is a chronic cardiovascular disease
Results from the buildup of cholesterol and other substances in the walls of arteries Gradually narrows arteries throughout the body Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

Artery partially blocked by plaque
Connective tissue Smooth muscle Epithelium Normal artery Artery partially blocked by plaque Figure 23.14 Figure A normal artery and an artery showing atherosclerosis

Heart disease: Involves inherited factors but Can be reduced by:
Not smoking Exercising regularly Eating a heart-healthy diet Student Misconceptions and Concerns 1. Students often develop an incorrect “mental model” of how atherosclerosis occurs. In a home, drainpipes grow narrower as materials accumulate on the inside surface. However, in atherosclerosis, the blood vessels narrow by an accumulation of materials within the walls. 2. Students often do not make the connection between iron in blood and iron used to build ships, automobiles, and buildings. Some of this confusion results from other similar names that indeed are not the same material (lead in pencils is not lead!). So, be sure to note that iron in blood is the same iron that forms rust on our cars and buildings in our cities. 3. Students often expect that the blood flowing through the heart supplies the heart muscle with oxygen. The need for coronary arteries and veins is not clear. The thickness of the walls of the heart do not permit efficient diffusion. Further, the oxygen content of blood in the right atrium and right ventricle is unlikely to meet this need. 4. Students often struggle to explain how blood is propelled up their legs to return to their hearts (perhaps as they sit during class). Frequently, students will suggest that the heart itself provides sufficient force to move blood completely around the body. However, if such pressures were generated, delicate capillaries would be destroyed. Other student hypotheses might include a negative, siphoning effect of the heart. (Although this can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thought and motivation to learn the answer. After completing the explanation, you might also note that it has been suggested that students will be more alert in class if they wiggle their legs. Challenge students to explain why this might work and why “locking the knees” when standing might have the opposite effect. Teaching Tips 1. When discussing mammalian and avian blood flow through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Reminding them that the sequence is right to left helps them to recall the correct atrial and ventricular sequences. 2. You may point out that in artwork, it is common to identify blood vessels in the arterial system as red and blood vessels in the venous system as blue. As biologists, such expectations can be so routine that we forget that we might need to point this out to our students. 3. Students often benefit from a quick connection between abstract ideas and a concrete example. When discussing the cardiac cycle, take the time to have students quickly take their own pulse as they are seated in class. Simply counting the beats in 15 seconds and multiplying by four will help them relate the lecture directly to themselves. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander. 4. If you had the students take their own pulses, this might be a good time to stimulate their curiosity. Students could be encouraged to learn more about how their heart rates vary during a day by comparing their pulse upon arrival to class versus in the middle of class (to compare the effects of exercise) and, if they consume caffeinated beverages, before and after consumption. 5. Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen poor blood, the pulmonary artery transports low oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or towards the heart). The structure of arteries better resists the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. 6. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty, simply by lifting up the hands to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 7. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand”, students might better understand the propulsive forces moving venous blood back to the heart. 8. Students might wonder why they are discouraged from swimming soon after eating a meal. As the authors point out, blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming on a full stomach is that even a small amount of vomit could clog an air passageway. 9. If you have a small fiber-optic lamp available, it is interesting to shine the light on your fingertips in a darkened room and see your fingers glow red. It is a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 10. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, consider consulting human anatomy and physiology textbooks. Searching the American Heart Association website at and using the key word aspirin will generate many current and related articles. 11. Cardiovascular disease does not only affect the blood vessels of the heart and brain. Many of the same risk factors that promote cardiovascular disease are associated with erectile dysfunction (the inability to get and keep an erection).

UNIFYING CONCEPTS OF ANIMAL RESPIRATION
Cellular respiration: Uses oxygen and glucose Produces water, carbon dioxide, and usable energy in the form of ATP Cells using cellular respiration: Need a constant supply of oxygen Must continuously dispose of CO2 The respiratory system promotes this gas exchange. Student Misconceptions and Concerns 1. As the authors note, it is important to distinguish between the uses of the word “respiration” in the context of the whole organism (breathing) versus in the context of cells (cellular respiration). 2. Respiratory structures such as gills and lungs are highly branched, reflecting an adaptation to increase the surface area and ultimately the surface-to-volume ratio of the animal. Students might not realize the common principles of adaptations to increase surface-to-volume ratios in the circulatory system (e.g., small size of red blood cells and tiny size of capillaries) and the highly branched respiratory structures. You might consider expanding on this principle as you address other systems that reflect such adaptations (e.g., greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates that includes many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs. 2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. 3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation! 4. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.

O2 CO2 Environment Cell C6H12O6 6 O2 6 CO2 6 H2O ATP Cellular
respiration Glucose Oxygen Carbon dioxide Water Energy Figure 23.UN1 Figure 23.UN1 Summary:gas exchange

The Structure and Function of Respiratory Surfaces
Animals can get oxygen from: The atmosphere, about 21% oxygen Bodies of water, about 3–5% oxygen Gas exchange occurs at the respiratory surface, which must be: Large enough to take up oxygen for every cell in the body Adapted to the lifestyle of the organism © 2010 Pearson Education, Inc. Student Misconceptions and Concerns 1. As the authors note, it is important to distinguish between the uses of the word “respiration” in the context of the whole organism (breathing) versus in the context of cells (cellular respiration). 2. Respiratory structures such as gills and lungs are highly branched, reflecting an adaptation to increase the surface area and ultimately the surface-to-volume ratio of the animal. Students might not realize the common principles of adaptations to increase surface-to-volume ratios in the circulatory system (e.g., small size of red blood cells and tiny size of capillaries) and the highly branched respiratory structures. You might consider expanding on this principle as you address other systems that reflect such adaptations (e.g., greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates that includes many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs. 2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. 3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation! 4. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.

In most land-dwelling animals, the respiratory surfaces are:
Folded into the body Open to the air only through narrow tubes Student Misconceptions and Concerns 1. As the authors note, it is important to distinguish between the uses of the word “respiration” in the context of the whole organism (breathing) versus in the context of cells (cellular respiration). 2. Respiratory structures such as gills and lungs are highly branched, reflecting an adaptation to increase the surface area and ultimately the surface-to-volume ratio of the animal. Students might not realize the common principles of adaptations to increase surface-to-volume ratios in the circulatory system (e.g., small size of red blood cells and tiny size of capillaries) and the highly branched respiratory structures. You might consider expanding on this principle as you address other systems that reflect such adaptations (e.g., greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates that includes many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs. 2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. 3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation! 4. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.

Body surface Respiratory surface CO2 O2 (within lung) O2 CO2 Capillary
(b) Lungs Figure 23.16b Figure 23.16b Respiratory surfaces: lungs

Lungs are: The most common respiratory surface of terrestrial organisms Located in only one part of the body The circulatory system transports oxygen from the respiratory surface to the rest of the body. Student Misconceptions and Concerns 1. As the authors note, it is important to distinguish between the uses of the word “respiration” in the context of the whole organism (breathing) versus in the context of cells (cellular respiration). 2. Respiratory structures such as gills and lungs are highly branched, reflecting an adaptation to increase the surface area and ultimately the surface-to-volume ratio of the animal. Students might not realize the common principles of adaptations to increase surface-to-volume ratios in the circulatory system (e.g., small size of red blood cells and tiny size of capillaries) and the highly branched respiratory structures. You might consider expanding on this principle as you address other systems that reflect such adaptations (e.g., greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates that includes many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs. 2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. 3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation! 4. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.

RESPIRATORY ORGANS Skin (entire body surface) Gills (extensions of the
Tracheae (branching internal tubes) Lungs (localized internal organs) Gills Air pore Tracheae (internal tubes) Moist skin of a leech Gills of a sea slug Tracheae of a silk moth caterpillar Model of a pair of human lungs Figure 23.17 Figure Types of respiratory organs

THE HUMAN RESPIRATORY SYSTEM
The human respiratory system has three phases of gas exchange: Breathing Transport of oxygen from the lungs to the rest of the body via the circulatory system Removal of oxygen from the blood and release of CO2 into the blood by cells of the body Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

the circulatory system
Breathing CO2 Lung Transport of gases by the circulatory system Circulatory system Servicing of cells within the body tissues Mitochondria O2 CO2 Capillary Cell Figure Figure The three phases of gas exchange (Step 3)

The Structure and Function of the Human Respiratory System
Air moves sequentially from the mouth and nose: To the pharynx, where digestive and respiratory systems meet To the larynx (voice box) and trachea (windpipe) To the bronchi (one bronchus to each lung) To the bronchioles, the smallest branches of the tubes within the lungs and To the alveoli, the air sacs where gas exchange primarily occurs © 2010 Pearson Education, Inc. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Figure 23.19 Pharynx Esophagus To heart From heart Nasal cavity
Larynx (voice box) Trachea (windpipe) Left lung O2-rich blood O2-poor blood Right lung Bronchiole Bronchus Bronchiole CO2 O2 Diaphragm Alveoli Blood capillaries Heart (a) Overview of the human respiratory system (b) The structure of alveoli Figure 23.19 Figure The human respiratory system

Muscles in the voice box can stretch vocal cords within the larynx.
During exhalation, outgoing air can produce vocal sounds as air passes by the stretched vocal cords. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Taking a Breath Breathing is the alternating process of: Inhalation
Exhalation Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

During inhalation, the chest is expanded by the:
Upward movement of the ribs Downward movement of the diaphragm Air moves into the lungs: By negative pressure breathing As the air pressure in the lungs is lowered by the expansion of the chest Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Rib cage expands as rib muscles contract Rib cage gets smaller as
relax Air inhaled Air exhaled Lung Diaphragm contracts (moves down) Diaphragm relaxes (moves up) Inhalation (Air pressure is higher in atmosphere than in lungs.) Exhalation (Air pressure is lower in atmosphere than in lungs.) Figure 23.20 Figure How a human breathes

Breathing can be controlled:
Consciously, as you deliberately take a breath, or Unconsciously Breathing control centers in the brain stem: Automatically control breathing most of the time Regulate breathing rate in response to CO2 levels in the blood Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

contraction of muscles to increase breathing rate and depth.
Brain Breathing control centers in the brain monitor the rising CO2 levels in the blood. Breathing control centers Nerve signals trigger contraction of muscles to increase breathing rate and depth. CO2 levels in the blood rise as a result of exercise. Rib muscles Diaphragm Figure Figure Control centers in the brain that regulate breathing (Step 3)

The Role of Hemoglobin in Gas Transport
The human respiratory system: Takes in O2 Expels CO2, but Relies on the circulatory system to shuttle these gases between the lungs and the body’s cells Animation: CO2 From Blood to Lungs Animation: CO2 From Tissues to Blood Animation: O2 From Blood to Tissues Animation: O2 From Lungs to Blood Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Figure 23.22 CO2 in exhaled air O2 in inhaled air Air spaces Alveolus
Capillaries of lung CO2-rich, O2-poor blood O2-rich, CO2-poor blood Tissue capillaries Heart CO2 O2 CO2 O2 Tissue cells throughout body Figure 23.22 Figure Gas transport and exchange in the body

However, there is one problem with this simple gas delivery system.
Problem: Oxygen does not dissolve readily in blood. Solution: Oxygen is carried in hemoglobin molecules within red blood cells. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Heme group Iron atom O2 O2 loaded in lungs O2 unloaded in tissues O2
Polypeptide chain Figure 23.23 Figure Hemoglobin loading and unloading oxygen

A shortage of iron: Causes a decrease in the rate of hemoglobin synthesis Can lead to anemia Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

How Smoking Affects the Lungs
Breathing exposes your respiratory tissues to potentially damaging chemicals, including one of the worst pollutants, tobacco smoke. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Tobacco smoke: Irritates the cells that line the bronchi and trachea
Inhibits their ability to remove foreign substances from the airways Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Smoking: Kills half of all people who smoke, about 440,000 Americans every year, Causes 90% of all lung cancer (one of the deadliest forms of cancer) Causes more deaths than the combined total of: All accidents Alcohol and other drug abuse HIV Murders Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

(a) Healthy lungs (nonsmoker) (b) Cancerous lungs (smoker)
Heart (a) Healthy lungs (nonsmoker) (b) Cancerous lungs (smoker) Figure 23.24 Figure Healthy versus cancerous lungs

Evolution Connection: Choked Up
The Heimlich maneuver: Involves quick thrusts to the diaphragm Compresses the lungs Forces air rapidly out of the chest May dislodge food or other objects obstructing the breathing pathway © 2010 Pearson Education, Inc. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

The food and air passageways pass through a common tube in the rear of the pharynx.
Choking results when food or other substances get diverted from the food to the air pathway. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

The common passageway of food and air reflects the remodeling of the food passageway during the evolution of the respiratory system in shallow-water fishes. Choking is thus a consequence of the evolutionary remodeling of the throat. Student Misconceptions and Concerns 1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation! 2. Some basic models of the human diaphragm your students might have experienced do not represent the anatomy of the diaphragm properly. When relaxed, the diaphragm arches upward towards the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily. 3. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up? Teaching Tips 1. Students often confuse the structures and functions of the trachea and esophagus. You might therefore point out that the trachea has a structure and function like the hose of a vacuum cleaner. The rigid ribbed walls of the trachea keep the tube open as air is sucked through it. The esophagus, however, relies upon rhythmic changes in the shape of the walls (peristalsis) to push food toward the stomach. A stiff wall of an esophagus would inhibit this function. 2. Some of your students may have been taught to breathe deeply by actively extending their stomach outwards. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity). 3. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood. 4. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur. 5. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, making their movement up and out of our respiratory systems easier. Although students might have heard this advice, they might not have fully understood the mechanisms.

Figure 23.25 Figure Heimlich maneuver

Circulation and Respiration

Similar presentations

Presentation on theme: "Circulation and Respiration"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Circulation and Respiration

Similar presentations

Presentation on theme: "Circulation and Respiration"— Presentation transcript:

Similar presentations

About project

Feedback