Introductory Biology III

Introductory Biology III
BIOL 100C: Introductory Biology III The Respiratory System Dr. P. Narguizian Fall 2012 Principles of Biology

Education-Portal: Online Video
Gas Exchange in the Human Respiratory System

MECHANISMS OF GAS EXCHANGE
MECHANISMS OF GAS EXCHANGE Copyright © 2009 Pearson Education, Inc.

Overview: Gas exchange in an animal with lungs involves breathing, transport of gases, and exchange of gases with tissue cells Three phases of gas exchange Breathing Transport of oxygen and carbon dioxide in blood Body tissues take up oxygen and release carbon dioxide Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). 2. As the authors note, it is important to distinguish between the use of the word respiration in the context of the whole organism (breathing) and in the context of cells (cellular respiration). Teaching Tips 1. You may want to point out that in scientific artwork, it is common to identify blood vessels in the arterial system by coloring them red, and blood vessels in the venous system by coloring them blue. As experienced biologists, such expectations can be so routine that we forget that we might need to point this out to our students. Copyright © 2009 Pearson Education, Inc.

The three phases of gas exchange.
Breathing 1 CO2 Lung Circulatory system 2 Transport of gases by the circulatory system The three phases of gas exchange. Figure 22.1 The three phases of gas exchange. Mitochondria Exchange of gases with body cells O2 3 CO2 Capillary Cell

Animals exchange O2 and CO2 across moist body surfaces
Respiratory surfaces must be thin and moist for diffusion of O2 and CO2 Earthworms and other animals use their skin for gas exchange Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates 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 absence of lungs. Copyright © 2009 Pearson Education, Inc.

The entire outer skin of an earthworm serves as its respiratory surface.
Cut Cross section of respiratory surface (the outer skin) CO2 Capillaries Figure 22.2A The entire outer skin of an earthworm serves as its respiratory surface. O2

Animals exchange O2 and CO2 across moist body surfaces
Most animals have specialized body parts that promote gas exchange Gills in fish and amphibians Tracheal systems in arthropods Lungs in tetrapods that live on land Amphibians Reptiles Birds Mammals Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Salamanders in the family Plethodontidae are unusual terrestrial vertebrates 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 absence of lungs. Copyright © 2009 Pearson Education, Inc.

CO2 O2 Body surface Respiratory surface (gill) Capillary
Figure 22.2B Gills are extensions of the body surface that function in gas exchange with the surrounding water. Capillary CO2 Gills are extensions of the body surface that function in gas exchange with the surrounding water. O2

O2 CO2 Body surface Respiratory surface (air tubes) Body cells
The tracheal system of an insect consists of tubes that extend throughout the body. Body surface Respiratory surface (air tubes) Figure 22.C The tracheal system of an insect consists of tubes that extend throughout the body. O2 Body cells (no capillaries) CO2

CO2 O2 CO2 O2 Body surface Respiratory surface (within lung) Capillary
Lungs are internal thin-walled sacs. Body surface Respiratory surface (within lung) CO2 O2 Figure 22.D Lungs are internal thin-walled sacs. CO2 O2 Capillary

Gills are adapted for gas exchange in aquatic environments
Gills Are extensions of the body Increase the surface to volume ratio Increase the surface area for gas exchange Oxygen absorbed Carbon dioxide released Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Students struggling to recall the conditions that increase the oxygen content of water might benefit by picturing in their mind a scenario that includes all the best conditions. A pool at the base of a waterfall, generated from melting snow, has a very high oxygen content because the water is (a) fresh, (b) cool, and (c) turbulent. 2. As the authors note in Module 22.3, the basic principles of countercurrent exchange apply to the transfer of gases and temperature. Countercurrent exchange as it applies to temperature is addressed in Chapter 25. 3. Challenge your class to explain why fish gills do not work well in air. As noted in Modules 22.2 and 22.3, respiratory surfaces need to remain moist. In addition, 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 that gills are spaced like this in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area. Copyright © 2009 Pearson Education, Inc.

In a fish, gas exchange is enhanced by Ventilation of the gills (moving water past the gills) Countercurrent flow of water and blood Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Students struggling to recall the conditions that increase the oxygen content of water might benefit by picturing in their mind a scenario that includes all the best conditions. A pool at the base of a waterfall, generated from melting snow, has a very high oxygen content because the water is (a) fresh, (b) cool, and (c) turbulent. 2. As the authors note in Module 22.3, the basic principles of countercurrent exchange apply to the transfer of gases and temperature. Countercurrent exchange as it applies to temperature is addressed in Chapter 25. 3. Challenge your class to explain why fish gills do not work well in air. As noted in Modules 22.2 and 22.3, respiratory surfaces need to remain moist. In addition, 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 that gills are spaced like this in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area. Copyright © 2009 Pearson Education, Inc.

Cold water holds more oxygen than warm water Fresh water holds more oxygen than salt water Turbulent water holds more oxygen than still water Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Students struggling to recall the conditions that increase the oxygen content of water might benefit by picturing in their mind a scenario that includes all the best conditions. A pool at the base of a waterfall, generated from melting snow, has a very high oxygen content because the water is (a) fresh, (b) cool, and (c) turbulent. 2. As the authors note in Module 22.3, the basic principles of countercurrent exchange apply to the transfer of gases and temperature. Countercurrent exchange as it applies to temperature is addressed in Chapter 25. 3. Challenge your class to explain why fish gills do not work well in air. As noted in Modules 22.2 and 22.3, respiratory surfaces need to remain moist. In addition, 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 that gills are spaced like this in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area. Copyright © 2009 Pearson Education, Inc.

Blood flow in simplified capillary, showing % O2
Gill arch Oxygen-poor blood Oxygen-rich blood Lamella Direction of water flow Blood vessels Gill arch Operculum (gill cover) Water flow between lamellae Blood flow through capillaries in lamella Gill filaments Countercurrent exchange Water flow, showing % O2 Figure 22.3 The structure of fish gills. 100 70 40 15 Diffusion of O2 from water to blood 80 60 30 5 Blood flow in simplified capillary, showing % O2

The tracheal system of insects provides direct exchange between the air and body cells
Compared to water, using air to breathe has two big advantages Air contains higher concentrations of O2 Air is lighter and easier to move Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. 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, whatever insects do is automatically the most common animal adaptation! 2. In a very general sense, the tracheal system of insects is like the ductwork bringing outside air into the individual offices of a high-rise building. (But unlike a tracheal system, the air is removed from the building by another system.) Copyright © 2009 Pearson Education, Inc.

The tracheal system of insects provides direct exchange between the air and body cells
Air-breathing animals lose water through their respiratory surfaces Insect tracheal systems use tiny branching tubes This reduces water loss Air is piped directly to cells Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. 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, whatever insects do is automatically the most common animal adaptation! 2. In a very general sense, the tracheal system of insects is like the ductwork bringing outside air into the individual offices of a high-rise building. (But unlike a tracheal system, the air is removed from the building by another system.) Copyright © 2009 Pearson Education, Inc.

The tracheal system of an insect.
Air sacs Tracheae Opening for air The tracheal system of an insect. Body cell Air sac Tracheole Figure 22.4A The tracheal system of an insect. Trachea Body wall O2 CO2

EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land
Tetrapods seem to have evolved in shallow water Fossil fish with legs had lungs and gills Legs may have helped them lift up to gulp air The fossil fish Tiktaalik illustrates these air-breathing adaptations Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. As noted in Module 22.5, this may have been true of the first tetrapods as well. Copyright © 2009 Pearson Education, Inc.

EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land
The first tetrapods on land diverged into three major lineages Amphibians use small lungs and their body surfaces Nonbird reptiles have lower metabolic rates and simpler lungs Birds and mammals have higher metabolic rates and more complex lungs Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. As noted in Module 22.5, this may have been true of the first tetrapods as well. Copyright © 2009 Pearson Education, Inc.

In the human respiratory system, branching tubes convey air to lungs located in the chest cavity
In mammals, air is inhaled through the nostrils into the nasal cavity Air is filtered by hairs and mucus surfaces Air is warmed and moisturized Air is sampled for odors Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). 2. Students often confuse the structures and functions of the trachea and esophagus. To help them distinguish, 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. If the esophagus had stiff walls, it would not be able to perform this function. Teaching Tips 1. 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. If the balloon neck is stretched tightly, it will produce high-pitched sounds; when it is relaxed, it will produce lower pitched sounds. 2. 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 brachial system. A long, warm shower hydrates these mucus films, facilitating their movement up and out of our respiratory systems. Although students might have heard this advice, they might not have fully understood the mechanisms. Copyright © 2009 Pearson Education, Inc.

From the nasal cavity, air next passes To the pharynx Then larynx, past the vocal cords Into the trachea, held open by cartilage rings Into the paired bronchi Into bronchioles And finally to the alveoli, grapelike clusters of air sacs, where gas exchange occurs Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). 2. Students often confuse the structures and functions of the trachea and esophagus. To help them distinguish, 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. If the esophagus had stiff walls, it would not be able to perform this function. Teaching Tips 1. 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. If the balloon neck is stretched tightly, it will produce high-pitched sounds; when it is relaxed, it will produce lower pitched sounds. 2. 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 brachial system. A long, warm shower hydrates these mucus films, facilitating their movement up and out of our respiratory systems. Although students might have heard this advice, they might not have fully understood the mechanisms. Copyright © 2009 Pearson Education, Inc.

The anatomy of the human respiratory system.
Nasal cavity Pharynx (Esophagus) Larynx Left lung Trachea Right lung Bronchus Figure 22.6A The anatomy of the human respiratory system. Bronchiole Diaphragm (Heart)

Details of the structure of alveoli (right).
Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli Details of the structure of alveoli (right). Figure 22.6A Details of the structure of alveoli. Blood capillaries

Alveoli are well adapted for gas exchange High surface area of capillaries High surface area of alveoli In alveoli O2 diffuses into the blood CO2 diffuses out of the blood Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). 2. Students often confuse the structures and functions of the trachea and esophagus. To help them distinguish, 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. If the esophagus had stiff walls, it would not be able to perform this function. Teaching Tips 1. 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. If the balloon neck is stretched tightly, it will produce high-pitched sounds; when it is relaxed, it will produce lower pitched sounds. 2. 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 brachial system. A long, warm shower hydrates these mucus films, facilitating their movement up and out of our respiratory systems. Although students might have heard this advice, they might not have fully understood the mechanisms. Copyright © 2009 Pearson Education, Inc.

Scanning electron micrographs of the air spaces in alveoli (left) and the capillaries that envelop the alveoli (right). Figure 22.6B Scanning electron micrographs of the air spaces in alveoli (left) and the capillaries that envelop the alveoli (right).

Negative pressure breathing ventilates our lungs
Breathing is the alternate inhalation and exhalation of air (ventilation) Inhalation occurs when The rib cage expands The diaphragm moves downward The pressure around the lungs decreases And air is drawn into the respiratory tract Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. In its relaxed state, the human diaphragm is domed upward toward the heart. Contracting the diaphragm pushes down on the intestines and stomach, forcing the abdominal region outward. Thus, it can be more difficult to inhale after having consumed a large volume of food and/or drink. 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 them to take a deeper breath. (The answer: it allows the diaphragm to move down with less resistance from body organs in the abdominal cavity). Copyright © 2009 Pearson Education, Inc.

Exhalation occurs when The rib cage contracts The diaphragm moves upward The pressure around the lungs increases And air is forced out of the respiratory tract Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. In its relaxed state, the human diaphragm is domed upward toward the heart. Contracting the diaphragm pushes down on the intestines and stomach, forcing the abdominal region outward. Thus, it can be more difficult to inhale after having consumed a large volume of food and/or drink. 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 them to take a deeper breath. (The answer: it allows the diaphragm to move down with less resistance from body organs in the abdominal cavity). Copyright © 2009 Pearson Education, Inc.

smaller as rib muscles relax Air inhaled Air exhaled Lung
Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Air inhaled Air exhaled Lung Diaphragm Figure 22.8 Negative pressure breathing draws air into the lungs. Diaphragm contracts (moves down) Diaphragm relaxes (moves up) Inhalation Exhalation

Not all air is expelled during exhalation Some air still remains in the trachea, bronchi, bronchioles, and alveoli This remaining air is “dead air” Thus, inhalation mixes fresh air with dead air One-way flow of air in birds reduces dead air and increases their ability to obtain oxygen You can extend the region of dead air space by having students breathe in and out of their mouths and through a paper tube, such as that from a roll of paper towels. As they breathe out through the tube, exhaled air fills the tube. When they next breathe in, the first air they inhale will be the old air in the tube. Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. In its relaxed state, the human diaphragm is domed upward toward the heart. Contracting the diaphragm pushes down on the intestines and stomach, forcing the abdominal region outward. Thus, it can be more difficult to inhale after having consumed a large volume of food and/or drink. 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 them to take a deeper breath. (The answer: it allows the diaphragm to move down with less resistance from body organs in the abdominal cavity). Copyright © 2009 Pearson Education, Inc.

Breathing is automatically controlled
Breathing is usually under automatic control Breathing control centers in the brain sense and respond to CO2 levels in the blood A drop in blood pH increases the rate and depth of breathing The breathing control centers in the brain are based upon the concentration of carbon dioxide in the blood (and the resulting changes in pH). Challenge your students to explain why this system is usually sufficient to provide adequate levels of oxygen in the blood. (The by-product of aerobic respiration is carbon dioxide.) Student Misconceptions and Concerns 1. Respiratory structures such as gills, lungs, and insect tracheal systems 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 highly branched respiratory structures, as well as in the circulatory system (for example, the small size of red blood cells and tiny size of capillaries), discussed in detail in the next chapter. You might consider expanding on this principle as you address other systems that reflect such adaptations (for example, greater surface area of the digestive system for absorption of nutrients). Teaching Tips 1. As noted in Module 22.9, the breathing control centers in the brain are based upon the concentration of carbon dioxide in the blood (and the resulting changes in pH). Challenge your students to explain why this system is usually sufficient to provide adequate levels of oxygen in the blood. (The by-product of aerobic respiration is carbon dioxide.) Copyright © 2009 Pearson Education, Inc.

Cerebrospinal fluid Brain Pons 2 Breathing control centers respond to pH of blood 1 Nerve signals trigger contraction of muscles Medulla Control centers that regulate breathing respond to the pH of blood and nervous stimulation from sensors that detect CO2 and O2 levels. 3 Nerve signals indicating CO2 and O2 levels Figure 22.9 Control centers that regulate breathing respond to the pH of blood and nervous stimulation from sensors that detect CO2 and O2 levels. CO2 and O2 sensors in aorta Diaphragm Rib muscles

Blood transports respiratory gases
The heart pumps blood to two regions The right side pumps oxygen-poor blood to the lungs The left side pumps oxygen-rich blood to the body In the lungs, blood picks up O2 and drops off CO2 In the body tissues, blood drops off O2 and picks up CO2 Student Misconceptions and Concerns 1. Many students still struggle with the concept of diffusion as the main mechanism of gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of the blood in body tissues, but into the blood in the lungs. Why don’t these processes proceed in the opposite direction? 2. Many students struggle with fundamental aspects of fetal circulation and respiration. Students might assume that the mother’s blood flows through the umbilical cord into the fetus. Students might also expect that the fetus is somehow breathing air. Nobody likes to be embarrassed by ignorance, so gauging these and many other misconceptions can be a challenge. To better understand your students’ background knowledge consider giving a short quiz on fundamental points before lecturing on the subject. Teaching Tips 1. Figure is an especially helpful depiction of the movements of gases in the human respiratory system. The figure includes all of the main sites where oxygen is consumed, the alveoli where gas exchange occurs in the lungs, and the separate movement of oxygenated and deoxygenated blood through the heart. Copyright © 2009 Pearson Education, Inc.

Blood transports respiratory gases
Gases move from areas of higher concentration to areas of lower concentration Gases in the alveoli of the lungs have more O2 and less CO2 than gases the blood O2 moves from the alveoli of the lungs into the blood CO2 moves from the blood into the alveoli of the lungs The tissues have more CO2 and less O2 than in the blood CO2 moves from the tissues into the blood O2 moves from the blood into the tissues Student Misconceptions and Concerns 1. Many students still struggle with the concept of diffusion as the main mechanism of gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of the blood in body tissues, but into the blood in the lungs. Why don’t these processes proceed in the opposite direction? 2. Many students struggle with fundamental aspects of fetal circulation and respiration. Students might assume that the mother’s blood flows through the umbilical cord into the fetus. Students might also expect that the fetus is somehow breathing air. Nobody likes to be embarrassed by ignorance, so gauging these and many other misconceptions can be a challenge. To better understand your students’ background knowledge consider giving a short quiz on fundamental points before lecturing on the subject. Teaching Tips 1. Figure is an especially helpful depiction of the movements of gases in the human respiratory system. The figure includes all of the main sites where oxygen is consumed, the alveoli where gas exchange occurs in the lungs, and the separate movement of oxygenated and deoxygenated blood through the heart. Copyright © 2009 Pearson Education, Inc.

Gas transport and exchange in the body.
Exhaled air Inhaled air Alveolar epithelial cells Air spaces CO2 O2 CO2 O2 Alveolar capillaries CO2-rich, O2-poor blood O2-rich, CO2-poor blood Gas transport and exchange in the body. Tissue capillaries Heart Figure Gas transport and exchange in the body. CO2 O2 Interstitial fluid CO2 O2 Tissue cells throughout body

Hemoglobin carries O2, helps transport CO2, and buffers the blood
Most animals transport O2 bound to proteins called respiratory pigments Copper-containing pigment is used by Molluscs Arthropods Iron-containing hemoglobin Is used by almost all vertebrates and many invertebrates Transports oxygen, buffers blood, and transports CO2 Student Misconceptions and Concerns 1. Many students still struggle with the concept of diffusion as the main mechanism of gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of the blood in body tissues, but into the blood in the lungs. Why don’t these processes proceed in the opposite direction? 2. Many students struggle with fundamental aspects of fetal circulation and respiration. Students might assume that the mother’s blood flows through the umbilical cord into the fetus. Students might also expect that the fetus is somehow breathing air. Nobody likes to be embarrassed by ignorance, so gauging these and many other misconceptions can be a challenge. To better understand your students’ background knowledge consider giving a short quiz on fundamental points before lecturing on the subject. Teaching Tips 1. 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 like the rust formed by the reaction of oxygen and iron, blood is also red, due to the bonding of oxygen to iron in our red blood cells. Furthermore, the familiar “metal” taste we experience when we have a cut in our mouth is due to the presence of iron in our blood. Copyright © 2009 Pearson Education, Inc.

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

Hemoglobin carries O2, helps transport CO2, and buffers the blood
Most CO2 in the blood is transported as bicarbonate ions in the plasma Student Misconceptions and Concerns 1. Many students still struggle with the concept of diffusion as the main mechanism of gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of the blood in body tissues, but into the blood in the lungs. Why don’t these processes proceed in the opposite direction? 2. Many students struggle with fundamental aspects of fetal circulation and respiration. Students might assume that the mother’s blood flows through the umbilical cord into the fetus. Students might also expect that the fetus is somehow breathing air. Nobody likes to be embarrassed by ignorance, so gauging these and many other misconceptions can be a challenge. To better understand your students’ background knowledge consider giving a short quiz on fundamental points before lecturing on the subject. Teaching Tips 1. 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 like the rust formed by the reaction of oxygen and iron, blood is also red, due to the bonding of oxygen to iron in our red blood cells. Furthermore, the familiar “metal” taste we experience when we have a cut in our mouth is due to the presence of iron in our blood. Copyright © 2009 Pearson Education, Inc.

O2 CO2 (c) (d) (e) (f) (g) Gas exchange (a) (b) tissue cells
requires moist, thin often relies on (a) (b) for exchange of to transport gases between red blood cells contain O2 CO2 (c) (d) needed for waste product of mammals ventilate by binds and transports and (e) helps to (f) tissue cells (g) regulated by breathing control centers transport CO2 and buffer the blood

a. b. c. d. e. f. g. h.

100 Llama 80 Human 60 of hemoglobin (%) O2 saturation 40 20 20 40 60 80 100 P (mm Hg) O2

You should now be able to
Describe the three main phases of gas exchange in a human Describe four types of respiratory surfaces and the types of animals that use them Explain how breathing air compares to using water for gas exchange Copyright © 2009 Pearson Education, Inc.

You should now be able to
4. Describe the parts and functions of the human respiratory system Explain how blood transports gases between the lungs and tissues of the body Describe the functions of hemoglobin Copyright © 2009 Pearson Education, Inc.

Introductory Biology III

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