1. excretory system eliminates metabolic waste
Every organism must exchange energy and nutrients/wastes with surroundings
EXTERNAL ENVIRONMENT
respiratory system exchanges gases between the external environment and blood.
CO2
Food O2
Mouth
ANIMAL
digestive system acquires food and eliminates wastes B l o d
Respiratory system
Digestive system
Interstitial fluid
Heart
Nutrients
Circulatory system
circulatory system
- distributes gases,
nutrients, and wastes
throughout the body
- exchanges materials
between blood and
body cells through the
interstitial fluid
Body cells
Figure 20.13A A schematic representation showing indirect exchange between the environment and the cells of a complex animal
Urinary system
excretory system eliminates metabolic waste
Intestine
Anus
Unabsorbed matter (feces)
Metabolic waste products (urine) 1

2. Function of CV System
Circulatory systems facilitate exchange with all body tissues
All cells must
receive nutrients,
exchange gases, and
remove wastes.
Diffusion alone is inadequate for large and complex bodies.
In most animals, circulatory systems facilitate these exchanges.
Assists diffusion by moving materials between
surfaces of the body and Internal tissues.
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
© 2012 Pearson Education, Inc. 2

3. Simple Gastrovascular Cavity is Found in Cnidarians and Flatworms
Cnidarians = jellyfish and hydra
Notice only one opening in/out!
Gastrovascular cavity serves both in digestion and distribution of substances throughout body
This is adequate for these organisms as they are only two layers of cells thick - all cells can exchange materials directly with water.
polyp
medusa
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
© 2012 Pearson Education, Inc. 3

4. Flatworms - We’re so flat because we exchange materials directly with environment.
Only ONE entrance/exit! YIKES!!
Gastrovascular
cavity
Nerve cords
Mouth/Anus
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
Eyecups
Nervous
tissue clusters
Bilateral symmetry
© 2012 Pearson Education, Inc. 4

5. Mouth Gastrovascular cavity Diffusion Diffusion Diffusion Single cell
Small organisms have sufficient SA:volume ratio that they do not require a specialized circulatory system.
Mouth
Gastrovascular
cavity
Diffusion
Diffusion
Diffusion
Single cell
Two cell layers

6. Large, more complex organisms require a true circulatory system
Most animals use a true circulatory system that consists of a
circulatory fluid (blood),
muscular pump (heart), and
set of tubes (blood vessels) to carry the 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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
© 2012 Pearson Education, Inc. 6

7. EXTERNAL ENVIRONMENT
But large, complex organisms require true CV system to maintain sufficient SA:volume ratio
CO2
Food O2
Mouth
ANIMAL B l o d
Respiratory system
Digestive system
Interstitial fluid
Heart
Nutrients
Circulatory system
Body cells
Figure 20.13A A schematic representation showing indirect exchange between the environment and the cells of a complex animal
Urinary system
Intestine
Anus
Unabsorbed matter (feces)
Metabolic waste products (urine) 7

8. 2 Types of Circulatory Systems
Open circulatory systems are found in arthropods and many molluscs and consist of
a heart,
open-ended vessels, and
blood that directly bathes the cells and functions as the interstitial fluid.
Tubular 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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
Pores
© 2012 Pearson Education, Inc. 8

9. An open circulatory system. A closed circulatory system.
LE 42-3
Heart
Heart
Hemolymph in sinuses
surrounding organs
Interstitial
fluid
Small branch vessels
in each organ
Anterior
vessel
Lateral
vessel
Ostia
Dorsal vessel
(main heart)
Tubular heart
Auxiliary hearts
Ventral vessels
An open circulatory system.
A closed circulatory system.

10. Two Types of Circulatory Systems
Closed circulatory systems are found in vertebrates, earthworms, squids, and octopuses and consist of
a heart and
vessels that confine blood, keeping it distinct from interstitial 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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
© 2012 Pearson Education, Inc. 10

11. Three Types of Blood Vessels Found in CV Systems
1. Arteries carry blood away from the heart.
2. Veins return blood to the heart.
3. Capillaries convey blood between arteries and veins.
Capillary beds
Arteriole
Artery (O2-rich blood)
Venule
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the 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 water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. 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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
Vein
Atrium
Gill capillaries
Heart
Artery (O2-poor blood)
Ventricle
© 2012 Pearson Education, Inc. 11

12. Vertebrate cardiovascular systems reflect evolution
Closed circulatory systems may exhibit:
In single circulation blood moves
from gill capillaries,
to systemic (body) capillaries, and
back to the heart.
Blood pressure drops significantly as blood flows thru gill capillaries
Single circuit would never provide enough pressure to push blood thru the lungs and rest of body in a terresterial (land) animal.
Characteristic of fish.
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 12

13. Gill capillaries Heart: Ventricle Atrium Body capillaries Figure 23.2A
Figure 23.2A The single circulation and two-chambered heart of a fish
Body capillaries 13

14. REPTILES (EXCEPT BIRDS) Lung and skin capillaries
FISHES
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
Gill capillaries
Lung and skin capillaries
Lung capillaries
Lung capillaries
Gill
circulation
Pulmocutaneous
circuit
Right
systemic
aorta
Pulmonary
circuit
Pulmonary
circuit
Artery
Heart:
Ventricle (V)
Left
systemic
aorta A A A A A A
Atrium (A) V V V V V
Right
Left
Right
Left
Right
Left
Systemic
circulation
Systemic
circuit
Systemic
circuit
Vein
Systemic capillaries
Systemic capillaries
Systemic capillaries
Systemic capillaries
Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.

15. Double circulation double circulation consists of a separate
double circulation consists of a separate
pulmonary circuit (heart to lungs and back to heart)
systemic circuit (heart to body tissue and back to heart)
Found in land animals - amphibians, reptiles, birds, mammals
Allows for a second ‘push’ of blood returning from lungs to provide enough pressure for blood to travel without organism’s body.
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 15

16. Four Chambered hearts are essential for organism with high metabolic rates (energy demands)
Four-chambered hearts
are found in crocodilians, birds, and mammals and
consist of
two atria and
two ventricles.
Birds, mammals and crocodiles are warm-blooded (endotherms) and thus require much greater rates of cellular respiration (thus more O2) to meet energy demands
Prevents oxygen-rich and oxygen-poor blood from mixing and keeps pulmonary and systemic circuits completely separate
oxygen-rich and
oxygen-poor blood.
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 (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in 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. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
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, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. 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.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 16

17. Blood flow through the human CV circuits
Blood flow through the double circulatory system of humans
drains from the superior vena cava (from the head and arms) or inferior vena cava (from the lower trunk and legs) into the right atrium,
moves out to the lungs via the pulmonary artery,
returns to the left atrium through the pulmonary vein, and
leaves the heart through the aorta.
Teaching Tips
When discussing the way blood flows 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. Having them memorize this sequence as right-to-left helps students recall the correct atrial and ventricular sequences.
Animation: Path of Blood Flow in Mammals
© 2012 Pearson Education, Inc. 17

18. Capillaries of head, chest and arms Superior vena cava
Figure 23.3A 8
Capillaries of head, chest and arms
Superior vena cava
Pulmonary artery
Pulmonary artery
Aorta 9
Capillaries of right lung
Capillaries of left lung 2 7 2 3 3 5 4 10 4
Pulmonary vein
Pulmonary vein 6 1 9
Right atrium
Left atrium
Figure 23.3A Blood flow through the double circulation of the human cardiovascular system
Left ventricle
Right ventricle
Aorta
Inferior vena cava
Capillaries of abdominal region and legs 8 18

19. Pulmonary artery Aorta Anterior vena cava Pulmonary artery Right
LE 42-6
Pulmonary artery
Aorta
Anterior
vena cava
Pulmonary
artery
Right
atrium
Left
atrium
Pulmonary
veins
Pulmonary
veins
Semilunar
valve
Semilunar
valve
Atrioventricular
valve
Atrioventricular
valve
Posterior
vena cava
Right
ventricle
Left
ventricle

20. The Cardiac Cycle
The repeated contraction and relaxation of pumping blood is called the cardiac cycle. The cycle consists of two main phases.
During diastole, heart relaxes and all chambers fill with blood
During systole, heart contracts and blood flows
from atria into ventricles
Then from ventricles into arteries
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. Students often benefit from brief, concrete demonstrations of abstract ideas. When discussing the cardiac cycle, take the time to have students quickly take their own pulses as they are seated in class to help them relate the lecture topic to their own anatomy. 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.
2. Having students take their own pulses also provides an opportunity to stimulate further curiosity. You may want to assign students to measure and record the variation in their pulse rates during the day’s different activities, perhaps (a) upon arrival to a class and after 20 minutes sitting in the class, (b) before and after drinking coffee, or (c) prior to and during exercise.
© 2012 Pearson Education, Inc. 20

21. 23.4 The heart contracts and relaxes rhythmically
Cardiac output is the amount of blood pumped per minute from the ventricles.
Cardiac output = Heart rate x volume of blood pumped with each contraction
Heart rate = is the number of heart beats per minute.
Heart rate and cardiac output vary with physiological conditions
Athletes have high CO even with low heart rates due to increased blood volume acquired from training
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. Students often benefit from brief, concrete demonstrations of abstract ideas. When discussing the cardiac cycle, take the time to have students quickly take their own pulses as they are seated in class to help them relate the lecture topic to their own anatomy. 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.
2. Having students take their own pulses also provides an opportunity to stimulate further curiosity. You may want to assign students to measure and record the variation in their pulse rates during the day’s different activities, perhaps (a) upon arrival to a class and after 20 minutes sitting in the class, (b) before and after drinking coffee, or (c) prior to and during exercise.
© 2012 Pearson Education, Inc. 21

22. 23.5 The SA node sets the tempo of the heartbeat
The SA (sinoatrial) node
generates electrical signals in atria and
sets the rate of heart contractions.
Called the pacemaker of the heart
SA Node receives nervous signal info from central nervous system and relays these changes in heart rate to rest of heart to coordinate cardiac cycle and heart rate. 1
Signals from the SA node spread through the atria.
SA node (pacemaker)
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. The specialized junctions that promote signal conduction between cardiac cells are specifically identified in Figure 20.6 in Chapter 20.
2. Before explaining the functions of the SA node, consider asking your students to explain why the atria contract before the ventricles contract. Posing a question and asking for an explanation rather than simply lecturing students often generates a more active interest in the subject matter.
Right atrium
ECG
© 2012 Pearson Education, Inc. 22

23. STRUCTURE AND FUNCTION OF BLOOD VESSELS
STRUCTURE AND FUNCTION OF BLOOD VESSELS
© 2012 Pearson Education, Inc. 23

24. 23.7 The structure of blood vessels fits their functions
Capillaries
Function:
only vessels involved in exchange of solutes and fluid between blood and interstitial fluid.
Structure:
have thin walls consisting of a single layer of epithelial cells,
are narrow, about as wide as one red blood cell, and
Structure allows for increased surface area to facilitate gas and fluid exchange
Student Misconceptions and Concerns
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 toward the heart). Due to their structure, arteries are better able to resist the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant.
Teaching Tips
1. The photo in Figure 23.7A demonstrates the narrow width of capillaries. Notice that the diameter of the capillaries barely permits the passage of red blood cells. (Also note that Figure 23.7B shows a capillary diameter much greater than in the photograph.) Challenge your students to explain why such a small size is adaptive. (Answer: it increases the surface area of capillaries and places red blood cells adjacent to the capillary walls for efficient gas exchange.)
2. One function of the circulatory system that is rarely discussed is the transport of heat. Blood vessels near the surface of the body expand when the body is overheated, releasing some of this excess heat to the environment. Conversely, during periods of exposure to cold, blood is shunted away from the skin to conserve heat.
3. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
© 2012 Pearson Education, Inc. 24

25. Diffusion of molecules Interstitial fluid
Capillary
Red blood cell
Capillary
Figure 23.7A A capillary in smooth muscle tissue
Diffusion of molecules
Interstitial fluid
Tissue cell 25

26. 23.7 The structure of blood vessels fits their functions
Arteries and veins
are lined by a single layer of epithelial cells and
connective tissue layer and smooth muscle that allows these vessels to recoil after stretching.
Arteries:
Largest in diameter of all vessels
thickest layer of smooth muscle in their walls
Allows them to constrict and reduce blood flow
Deal with higher blood pressure and exhibit increased elasticity
Veins:
have one-way valves that restrict backward flow of blood.
Student Misconceptions and Concerns
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 toward the heart). Due to their structure, arteries are better able to resist the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant.
Teaching Tips
1. The photo in Figure 23.7A demonstrates the narrow width of capillaries. Notice that the diameter of the capillaries barely permits the passage of red blood cells. (Also note that Figure 23.7B shows a capillary diameter much greater than in the photograph.) Challenge your students to explain why such a small size is adaptive. (Answer: it increases the surface area of capillaries and places red blood cells adjacent to the capillary walls for efficient gas exchange.)
2. One function of the circulatory system that is rarely discussed is the transport of heat. Blood vessels near the surface of the body expand when the body is overheated, releasing some of this excess heat to the environment. Conversely, during periods of exposure to cold, blood is shunted away from the skin to conserve heat.
3. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
© 2012 Pearson Education, Inc. 26

27. Epithelium Basal lamina Capillary Valve Epithelium Epithelium
Figure 23.7C
Epithelium
Basal lamina
Capillary
Valve
Epithelium
Epithelium
Smooth muscle
Smooth muscle
Connective tissue
Connective tissue
Artery
Vein
Figure 23.7C Structural relationships of blood vessels
Arteriole
Venule 27

28. 23.8 Blood pressure and velocity
Blood pressure
is the force blood exerts on vessel walls,
depends on:
cardiac output (volume of blood and heart rate)
resistance of vessels to expansion
decreases as blood moves away from the heart.
Student Misconceptions and Concerns
Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart 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 thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!)
Teaching Tips
1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
2. 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 by simply lifting their hands up 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.
3. 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 may better understand the propulsive forces moving venous blood back to the heart.
© 2012 Pearson Education, Inc. 28

29. 23.8 Blood pressure and velocity
Blood pressure is
highest in arteries and
lowest in veins.
Blood pressure is measured as
systolic pressure — caused by ventricular contraction,
diastolic pressure — low pressure between contractions.
Student Misconceptions and Concerns
Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart 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 thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!)
Teaching Tips
1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
2. 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 by simply lifting their hands up 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.
3. 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 may better understand the propulsive forces moving venous blood back to the heart.
© 2012 Pearson Education, Inc. 29

30. Pressure (mm Hg) Velocity (cm/sec)
Figure 23.8A
120
Systolic pressure
100
Pressure (mm Hg) 80 60
Diastolic pressure 40 20
Relative sizes and numbers of blood vessels 50 40
Velocity (cm/sec) 30
Figure 23.8A Blood pressure and velocity in the blood vessels 20 10
Aorta
Veins
Arteries
Venules
Arterioles
Capillaries
Venae cavae 30

32. 23.8 Blood pressure and velocity reflect the structure and arrangement of blood vessels
How does blood travel against gravity, up legs?
Veins are squeezed by pressure from muscle contractions between
two muscles or
muscles and bone or skin.
One-way valves limit blood flow to one direction, toward the heart.
Direction of blood flow in vein
Valve (open)
Contracting skeletal muscle
Student Misconceptions and Concerns
Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart 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 thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!)
Teaching Tips
1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
2. 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 by simply lifting their hands up 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.
3. 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 may better understand the propulsive forces moving venous blood back to the heart.
Valve (closed)
© 2012 Pearson Education, Inc. 32

33. Measuring blood pressure can reveal cardiovascular problems
A typical blood pressure for a healthy young adult is about 120/70.
Hypertension is a serious cardiovascular problem in which blood pressure is persistent at or above
140 systolic and/or
90 diastolic.
Teaching Tips
Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure.
© 2012 Pearson Education, Inc. 33

34. 23.10 Smooth muscle controls the distribution of blood
Blood flow through capillaries is restricted by precapillary sphincters.
By opening and closing these precapillary sphincters, blood flow to particular regions can be increased or decreased.
Only about 5–10% of capillaries are open at one time.
Teaching Tips
Students might wonder why they are discouraged from swimming soon after eating a meal. 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 with a full stomach is more likely that even a small amount of vomit could clog an air passageway.
© 2012 Pearson Education, Inc. 34

35. Precapillary sphincters Thoroughfare channel
Figure 23.10
Precapillary sphincters
Thoroughfare channel
Arteriole
Venule
Capillaries 1
Sphincters are relaxed.
Thoroughfare channel
Figure The control of capillary blood flow by precapillary sphincters
Arteriole
Venule 2
Sphincters are contracted. 35

36. 23.11 Exchange of materials between blood and interstitial fluid occurs at capillaries
Substances leave blood and enter interstitial fluid by
diffusion (following concentration gradient) and
pressure-driven flow through clefts between epithelial cells.
Blood pressure forces fluid (water) out of capillaries at the arterial end.
Osmotic pressure draws in fluid (water) at the venous end.
Teaching Tips
1. Figure 23.11B depicts the movements of fluid out of and back into capillaries because of changes in osmotic pressure. The text references Module 24.3 for further discussion of the role of the lymphatic system in fluid removal. If you do not plan on addressing Chapter 24, consider including the role of lymphatic vessels in your discussion of Chapter 23.
2. Students who have little practice interpreting electron micrographs might benefit from a closer analysis of Figure 23.11A, in which an electron micrograph is paired with explanatory figure. For example, simply recognizing nuclei in micrographs can be an important starting point in interpreting cellular details and gaining a sense of scale.
© 2012 Pearson Education, Inc. 36

37. LE 42-14 Tissue cell INTERSTITIAL FLUID Net fluid movement out
movement in
Capillary
Capillary
Red
blood
cell
15 µm
Direction of
blood flow
Blood pressure
Osmotic pressure
Inward flow
Pressure
Outward flow
Arterial end of capillary
Venous end

38. Glucose, O2, and other nutrients have greatest concentration in blood at arterial end so they move out by diffusion
Water moves by net effect of blood versus osmotic pressure
CO2 and other wastes have greatest concentration in interstitial fluid at venous end so they move in by diffusion

39. STRUCTURE AND FUNCTION OF BLOOD
STRUCTURE AND FUNCTION OF BLOOD
© 2012 Pearson Education, Inc. 39

40. 23.12 Blood consists of red and white blood cells suspended in plasma
Plasma (55%)
Cellular elements (45%)
Constituent
Major functions
Cell type
Number per L (mm3) of blood)
Functions
Water
Solvent for carrying other substances
Centrifuged blood sample
Red blood cells (erythrocytes)
5–6 million
Transport of O2 and some CO2
Ions (blood electrolytes)
Osmotic balance, pH buffering, and maintaining ion concentration of interstitial fluid
Sodium Potassium Calcium Magnesium Chloride Bicarbonate
White blood cells (leukocytes)
5,000–10,000
Defense and immunity
Plasma proteins
Student Misconceptions and Concerns
1. Students with limited backgrounds in anatomy and physiology might not appreciate the diverse functions of plasma, instead thinking of blood as a transporter of oxygen and carbon dioxide. Figure lists the many functions performed by plasma.
2. Students might have heard about blood thinners, thinking that somehow these substances make blood more fluid (like watering down syrup). The term actually refers to substances that make blood clotting less likely. Anticoagulants are specifically addressed in Module
Teaching Tips
1. If you have a small fiber-optic lamp available, shining the light through your fingertips in a darkened room creates a red glow. This provides a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies.
2. Discuss the relationship between the structure and functions of erythrocytes. In Module 23.12, the authors note that the absence of a nucleus permits these cells to carry a greater amount of hemoglobin. But why is an erythrocyte dented in the middle? Wouldn’t it seem more likely to be shaped like a hockey puck? The indentation in the center of an erythrocyte might increase its flexibility, permitting easier passage through small capillaries. Encourage students to contribute other ideas on the adaptive advantages of this unique shape (including a higher surface-to-volume ratio).
3. 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, search the American Heart Association website at using the key word aspirin.
Osmotic balance and pH buffering
Basophils
Lymphocytes
Fibrinogen
Clotting
Eosinophils
Immunoglobulins (antibodies)
Defense
Substances transported by blood
Neutrophils
Monocytes
Nutrients (e.g., glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones
Platelets
250,000– 400,000
Blood clotting 40

41. Figure 23.13
Figure Human red blood cells 41

42. New Blood Cells are generated in bone marrow from stem cells
Multipotent stem cells
are unspecialized and
replace themselves throughout the life of an organism.
Multipotent stem cells can differentiate into two main types of stem cells.
Lymphoid stem cells can in turn produce two types of lymphocytes (T- and B-cells), which function in the immune system.
Myeloid stem cells can differentiate into
erythrocytes,
other white blood cells, and
platelets.
Student Misconceptions and Concerns
Students might have heard about blood thinners, thinking that somehow these substances make blood more fluid (like watering down syrup). The term actually refers to substances that make blood clotting less likely. Anticoagulants are specifically addressed in Module
Teaching Tips
1. Advances in stem cell research continue, along with political controversy over whether or not such research should be funded by the federal government. You may want to consider bringing recent articles about stem cell research to class, or encourage your students to find a recent article about some aspect of stem cells and it to you.
2. 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, search the American Heart Association website at using the key word aspirin.
© 2012 Pearson Education, Inc. 42

43. Multipotent stem cells (in bone marrow)
Figure 23.15
Multipotent stem cells (in bone marrow)
Lymphoid stem cells
Myeloid stem cells
Basophils
Erythrocytes
Figure Differentiation of blood cells from stem cells
Platelets
Eosinophils
Lymphocytes
Monocytes
Neutrophils 43

44. Figure 50.17 Control of Blood Pressure through Local and Systemic Mechanisms

45. Figure 50.18 Regulating Cardiac Output