1. UNIFYING CONCEPTS OF ANIMAL RESPIRATION
Ch 23 part II Respiration
UNIFYING CONCEPTS OF ANIMAL RESPIRATION
Cells using cellular respiration need a steady supply of oxygen and must continuously dispose of CO2
The respiratory system promotes this gas exchange. O2
CO2
Environment
Cell
C6H12O6
6 O2
6 CO2
6 H2O
ATP
Cellular
respiration
Glucose
Oxygen
Carbon
dioxide
Water
Energy
Student Misconceptions and Concerns
1. As the authors note, it is important to distinguish between the uses of the word respiration in the context of the whole organism (breathing) versus in the context of cells (cellular respiration).
2. Respiratory structures such as gills, 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 include many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs.
2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. This appears to be true of the first tetrapods such as the new fossil fish-amphibian Tiktaalik.
3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation!
4. In a very general sense, the tracheal system of insects is like the ductwork distributing 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.)
5. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other out of water. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area.
© 2013 Pearson Education, Inc. 1

2. The Human Respiratory System
Ch 23 part II Respiration
The Human Respiratory System
Gas exchange occurs at the respiratory surface within the lungs
A large, moist internal surface folded into the body
open to the air only through narrow tubes
The circulatory system transports gases between the respiratory surface (alveoli) and the rest of the body
Lungs
(localized internal organs)
Model of a pair of human lungs
Student Misconceptions and Concerns
1. As the authors note, it is important to distinguish between the uses of the word respiration in the context of the whole organism (breathing) versus in the context of cells (cellular respiration).
2. Respiratory structures such as gills, 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 include many species that survive mainly on land as adults, yet have no lungs. The adults acquire all of their oxygen through their skin. Consider discussing with your class how this is possible. Their relatively small size, slow metabolic rates, preference for cool environments, and minimal physical activity all permit the lack of lungs.
2. Many aquatic amphibians, such as the axolotl salamander, use gills, lungs, and skin surfaces for gas exchange. This appears to be true of the first tetrapods such as the new fossil fish-amphibian Tiktaalik.
3. You might mention to your class that most animals use tracheal systems. After all, insects are by far the dominant type of animal on Earth (at least 70% of all known species). Therefore, what insects do is automatically the most common animal adaptation!
4. In a very general sense, the tracheal system of insects is like the ductwork distributing 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.)
5. Challenge your class to explain why fish gills do not work well in air. First, respiratory surfaces need to remain moist. Second, the surface area of the gills is greatly reduced as the filaments adhere to each other out of water. You can visually demonstrate this point by simply lifting your hand and spreading your fingers apart, noting the spaced arrangement of gills in water. In air (bring your fingers together), the filaments adhere into one larger mass with less surface area. 2

3. The Human Respiratory System
Ch 23 part II Respiration
The Human Respiratory System
The human respiratory system has three phases of gas exchange:
breathing, the ventilation of the lungs by alternate inhalation and exhalation,
transport of oxygen from the lungs to the rest of the body via the circulatory system, and
diffusion of oxygen from the blood and release of CO2 into the blood by cells of the body.
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.)
© 2013 Pearson Education, Inc. 3

4. Pulmonary circuit Heart Venae cavae Systemic circuit
Figure 23.UN02
CO2 O2
Capillaries
Pulmonary
arteries
Pulmonary
veins
Pulmonary circuit
Heart
Venae cavae
Aorta
Systemic circuit
Veins
Arteries
Venules
Arterioles
O2-rich blood
Capillaries
O2-poor blood

5. The Human Respiratory System
has a series of passageways that carry air into and out of the lungs
It warms & moistens the air moving through it
It is lined by epithelial cells:
mucus traps dust and microorganisms
cilia sweep mucus up toward pharynx
© 2013 Pearson Education, Inc.

6. Mouth – into oral cavity
Ch 23 part II Respiration
Human respiratory system
common chamber for air & food
Air
Mouth – into oral cavity
Nostrils – into nasal cavity
Pharynx
Air filtered by hairs & mucus
Air warmed & humidified
Esophagus
food to stomach
Larynx (voice box)
Muscles in the voice box stretch vocal chords & exhalation passes air over them to produce sounds
Trachea (windpipe)
Flexible tube with walls reinforced with semicircular bands of stiff hyaline cartilage

7. Lead to alveoli (pl.) (air sacs)
Ch 23 part II Respiration
In the lungs
(to left lung)
Bronchus
Gas exchange
Bronchioles
Lead to alveoli (pl.) (air sacs)
Trachea
Bronchus
(to right lung)
Bronchioles
In the lung the bronchi branch into numerous, even smaller tubes called bronchioles

8. (a) Overview of the human respiratory system
Ch 23 part II Respiration
Figure 23.19a
Pharynx
Nasal cavity
Esophagus
Larynx (voice box)
Left lung
Trachea (windpipe)
Right lung
Bronchus
Bronchiole
Diaphragm
Heart
Figure The human respiratory system: overview (part 1)
(a) Overview of the human respiratory system

9. Respiratory surface is thin and moist & allows for rapid diffusion
Ch 23 part II Respiration
Figure 23.19b
Respiratory surface is thin and moist & allows for rapid diffusion
Alveoli: simple squamous epithelium
Pulmonary capillaries: simple squamous epithelium To
heart
From
heart
O2-rich
blood
O2-poor
blood
Bronchiole O2
CO2
Pulmonary capillaries surround alveoli
Alveoli
Blood
capillaries
(b) The structure of alveoli (air sacs)
1.5 to 2.5 million are packed into
each lung
Figure The human respiratory system: alveoli (part 2)

10. Gas exchange between alveoli and capillaries
from pulmonary artery
alveolar membrane
respiratory membrane
to pulmonary vein
(air)
CO2 O2
capillary
fluid
Oxygen diffuses into red blood cells
Carbon dioxide diffuses into alveolus
Gas exchange between alveoli and capillaries
Gases can dissolve & diffuse between the lungs and the circulatory system

11. Lungs Lungs are protected within an airtight chest cavity
The chest cavity is bound by:
neck muscles & connective tissue on the top
muscular thin diaphragm on the bottom
The rib cage surrounds and protects the lungs

12. Ch 23 part II Respiration
Taking a Breath
Breathing is the alternating process of inhalation and exhalation.
During inhalation
upward movement of the ribs
downward movement of the diaphragm (contraction)
volume of the lungs increases/chest is expanded
Air pressure in lungs drops below air pressure of atmosphere
Air moves into the lungs by negative pressure breathing (air moves from high to low pressure)
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.) 12

13. Ch 23 part II Respiration
Taking a Breath
Automatic exhalation of air occurs when muscles that cause inhalation are relaxed and the chest cavity is restricted
inward movement of the ribs
upward movement of the diaphragm
the volume of the lungs decreases
air pressure in the lungs increases
air moves out of the respiratory system
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.) 13

14. Inhalation Exhalation
Ch 23 part II Respiration
Figure 23.20
Rib cage gets
smaller as
rib muscles
relax
Rib cage
expands as
rib muscles
contract
Air
inhaled
Air
exhaled
Lung
Diaphragm
contracts
(moves
down)
Diaphragm
relaxes
(moves up)
Inhalation
(Air pressure is higher in atmosphere than in lungs.)
Exhalation
(Air pressure is lower in atmosphere than in lungs.)
Figure How a human breathes

15. Taking a Breath Breathing can be controlled
Ch 23 part II Respiration
Taking a Breath
Breathing can be controlled
consciously, as you deliberately take a breath, or
unconsciously
Breathing control centers in the brain stem
automatically control breathing most of the time
regulate breathing rate in response to CO2 levels in the blood
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.)
© 2013 Pearson Education, Inc. 15

16. Signals a need for more oxygen
Ch 23 part II Respiration
Figure
Brain
Breathing control
centers 1
CO2 levels in the
blood rise as a
result of exercise. 2
Breathing control
centers in the brain
monitor the rising CO2 levels in the blood.
Signals a need for more oxygen 3
Nerve signals trigger contraction of muscles to increase breathing
rate and depth.
Figure Control centers in the brain that regulate breathing (step 3)
Rib muscles
Diaphragm

17. The Role of Hemoglobin in Gas Transport
Ch 23 part II Respiration
The Role of Hemoglobin in Gas Transport
CO2 in
exhaled air
O2 in
inhaled air
Air spaces
The human respiratory system
takes in O2
expels CO2, but
relies on the circulatory system to shuttle these gases between the lungs and the body’s cells.
Alveolus
CO2 O2 O2
CO2
Capillaries
of lung
CO2-rich,
O2-poor
blood
O2-rich,
CO2-poor
blood
Heart
Tissue
capillaries
CO2 O2
CO2
Interstitial fluid O2
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.)
Tissue cells throughout body 17

18. The Role of Hemoglobin in Gas Transport
Ch 23 part II Respiration
The Role of Hemoglobin in Gas Transport
Oxygen does not readily dissolve in blood.
Solution: Oxygen is carried in hemoglobin molecules within red blood cells
Heme
group
Iron
atom O2
O2 loaded
in lungs O2
O2 unloaded
in tissues
A shortage of iron
causes a decrease in the rate of hemoglobin synthesis and
can lead to anemia.
Polypeptide chain 18

19. How Smoking Affects the Lungs
Ch 23 part II Respiration
How Smoking Affects the Lungs
Breathing exposes your respiratory tissues to potentially damaging chemicals
Tobacco smoke
damages the cells that line the bronchi and trachea
interferes with the normal cleansing mechanism of the respiratory system: more toxin-laden smoke particles reach & damage the lungs’ alveoli
Student Misconceptions and Concerns
1. The exchange of oxygen and carbon dioxide in the lungs does not result in exhaled air depleted of all oxygen and blood with no carbon dioxide remaining. However, students may think that this is true. Instead, gas exchange in the lungs results in proportional changes. You may point out to your students that if the air we exhale had no oxygen, there would be little benefit to mouth-to-mouth resuscitation!
2. Many students still struggle with diffusion as the main mechanism for gas transport. Before discussing gas transport, ask your class to explain why oxygen moves out of blood in body tissues and into blood in the lungs. Why doesn’t the process get mixed up?
3. Students might misunderstand how the cilia lining our respiratory passages work. Cilia do not filter the air like a comb. Instead, cilia are covered by a layer of mucus. Dust particles adhere to sticky mucus, which is then swept up the respiratory tract by the cilia. If students clear their throats, they will identify the fate of this mucus. We swallow after clearing our throats!
4. 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 propel food toward the stomach. If the esophagus had stiff walls, it would not be able to perform this function.
5. Some basic models of the human diaphragm your students might have experienced do not properly represent the anatomy of the diaphragm. When relaxed, the diaphragm arches upward toward the heart. When contracted, the diaphragm flattens. This dropping of the diaphragm compresses the stomach, moving it downward and outward. After a large meal, it is more difficult to breathe because a full stomach does not move as easily.
Teaching Tips
1. Some of your students may have been taught to breathe deeply by actively extending their stomach outward. Ask your class to explain why this permits a deeper breath (it allows the diaphragm to move even lower with less resistance from body organs in the abdominal cavity).
2. Students are often surprised to learn that the mineral iron in our diets is the same iron we use for building automobiles, pots, and pans. You might wish to point out that just as rust forms by the reaction of oxygen and iron, the red color of blood is due to the bonding of oxygen to iron in our red blood cells. Further, when we have a cut in our mouth, the familiar metal taste may well be due to the presence of iron in our blood.
3. The basic principles of the vocal cords can be demonstrated by inflating a balloon and letting air out while stretching the neck of the balloon. As the balloon neck is tightly stretched, high-pitched sounds are produced. When the neck is more relaxed, lower-pitched sounds occur.
4. Students often appreciate explanations that help them understand their own experiences. When we struggle with respiratory infections or allergies, especially when the air is dry, thick mucus accumulates in our branchial system. A long, warm shower hydrates these mucus films, 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. (Sipping hot tea or soup also helps to hydrate these mucus surfaces.)
© 2013 Pearson Education, Inc. 19

20. How Smoking Affects the Lungs
Ch 23 part II Respiration
How Smoking Affects the Lungs
Smoking
kills half of all people who smoke, about 440,000 Americans every year,
causes 90% of all lung cancer (one of the deadliest forms of cancer), and
causes more deaths than the combined total of
all accidents,
alcohol and other drug abuse,
HIV, and
murders.
(a) Healthy lung (nonsmoker)
(b) Cancerous lung (smoker) 20