Chapter 48: Gas Exchange in Animals CHAPTER 48 Gas Exchange in Animals

Chapter 48: Gas Exchange in Animals

CHAPTER 48Gas Exchange in Animals


Chapter 48: Gas Exchange in AnimalsRespiratory Gas ExchangeRespiratory Gas Exchange

Respiratory Adaptations for Gas ExchangRespiratory Adaptations for Gas Exchangee

Mammalian Lungs and Gas ExchangeMammalian Lungs and Gas Exchange

Blood Transport of Respiratory GasesBlood Transport of Respiratory Gases

Regulating Breathing to Supply ORegulating Breathing to Supply O22


Respiratory Gas Exchange• Most cells require a constant supply of Most cells require a constant supply of

OO22 and continuous removal of CO and continuous removal of CO22. .

• These respiratory gases exchange These respiratory gases exchange between the body fluids of an animal between the body fluids of an animal and its environment by diffusion.and its environment by diffusion.

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Respiratory Gas Exchange • In aquatic animals, gas exchange is In aquatic animals, gas exchange is

limited by low diffusion rate and low Olimited by low diffusion rate and low O2 2

level in water. level in water. • As water temperature rises, aquatic As water temperature rises, aquatic

animals face a double bind in that Oanimals face a double bind in that O22 in water decreases, but in water decreases, but

• Their metabolism and work required to Their metabolism and work required to move water over gas exchange move water over gas exchange surfaces increases. surfaces increases.

Review Figure 48.2Review Figure 48.244


Figure 48.2

Figure 48.2Figure 48.2

figure 48-02.jpg


Respiratory Adaptations for Gas Exchange• The evolution of large animals with high The evolution of large animals with high

metabolic rates required adaptations to metabolic rates required adaptations to maximize respiratory gas diffusion rates:maximize respiratory gas diffusion rates:

• Increasing surface areas Increasing surface areas • maximizing partial pressure gradientsmaximizing partial pressure gradients• decreasing their thicknessdecreasing their thickness• ventilating the outer surface with gasesventilating the outer surface with gases• perfusing the inner surface with blood. perfusing the inner surface with blood.


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Figure 48.4


figure 48-04.jpg


Respiratory Adaptations for Gas Exchange • Insects distribute air throughout their Insects distribute air throughout their

bodies in a system of tracheae, bodies in a system of tracheae, tracheoles, and air capillaries. tracheoles, and air capillaries.


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Figure 48.5


figure 48-05.jpg


Respiratory Adaptations for Gas Exchange • Fish have maximized gas exchange Fish have maximized gas exchange

rates by having large gas exchange rates by having large gas exchange surface areas ventilated continuously surface areas ventilated continuously and unidirectionally with fresh water. and unidirectionally with fresh water.

• Countercurrent blood flow helps Countercurrent blood flow helps increase gas exchange efficiency. increase gas exchange efficiency.

Review Figures 48.6, 48.7Review Figures 48.6, 48.7

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Figure 48.6


figure 48-06.jpg


Figure 48.7


figure 48-07.jpg


Respiratory Adaptations for Gas Exchange • The gas exchange system of birds The gas exchange system of birds

includes air sacs that communicate includes air sacs that communicate with the lungs but are not used for gas with the lungs but are not used for gas exchange. exchange.

• Air flows unidirectionally through bird Air flows unidirectionally through bird lungs in parabronchi. lungs in parabronchi.

• Gases are exchanged in air capillaries Gases are exchanged in air capillaries running between parabronchi. running between parabronchi.

Review Figures 48.8, 48.9Review Figures 48.8, 48.9

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Figure 48.8


figure 48-08.jpg


Figure 48.9


figure 48-09.jpg


Respiratory Adaptations for Gas Exchange • Each breath of air remains in the bird Each breath of air remains in the bird

respiratory system for two breathing respiratory system for two breathing cycles. cycles.

• The air sacs work as bellows to supply The air sacs work as bellows to supply the air capillaries with a continuous, the air capillaries with a continuous, unidirectional flow of fresh air. unidirectional flow of fresh air.


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Figure 48.10 – Part 1

Figure 48.10 – Part 1Figure 48.10 – Part 1

figure 48-10a.jpg




figure 48-10b.jpg


Respiratory Adaptations for Gas Exchange • Breathing in vertebrates other than Breathing in vertebrates other than

birds is tidal, thus less efficient than birds is tidal, thus less efficient than gas exchange in fishes or birds. gas exchange in fishes or birds.

• Even though the volume of air Even though the volume of air exchanged with each breath can vary exchanged with each breath can vary considerably, inhaled air is always considerably, inhaled air is always mixed with stale air. mixed with stale air.


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Figure 48.11


figure 48-11.jpg


Mammalian Lungs and Gas Exchange• In mammalian lungs, the gas In mammalian lungs, the gas

exchange surface area provided by the exchange surface area provided by the millions of alveoli is enormous, and millions of alveoli is enormous, and

• The diffusion path length between the The diffusion path length between the air and perfusing blood is very short. air and perfusing blood is very short.


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figure 48-12a.jpg




figure 48-12b.jpg


Mammalian Lungs and Gas Exchange • Surface tension in the alveoli would Surface tension in the alveoli would

make their inflation difficult if the make their inflation difficult if the lungs did not produce surfactant.lungs did not produce surfactant.

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Mammalian Lungs and Gas Exchange • Inhalation occurs when contractions of Inhalation occurs when contractions of

the diaphragm and intercostal muscles the diaphragm and intercostal muscles create negative pressure in the thoracic create negative pressure in the thoracic cavity. cavity.

• Relaxation of the diaphragm and some Relaxation of the diaphragm and some intercostal muscles and contraction of intercostal muscles and contraction of other intercostal muscles increases other intercostal muscles increases pressure in the thoracic cavity causing pressure in the thoracic cavity causing exhalation. exhalation.


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Figure 48.13


figure 48-13.jpg


Blood Transport of Respiratory Gases• Oxygen is reversibly bound to hemoglobin in Oxygen is reversibly bound to hemoglobin in

red blood cells. red blood cells.

• Each hemoglobin molecule can carry four OEach hemoglobin molecule can carry four O2 2

molecules maximum. molecules maximum. • Because of positive cooperativity, affinity of Because of positive cooperativity, affinity of

hemoglobin for Ohemoglobin for O22 depends on the <P depends on the <POO22 to to

which the hemoglobin is exposed. which the hemoglobin is exposed.

• Therefore, hemoglobin gives up OTherefore, hemoglobin gives up O22 in in metabolically active tissues and picks it up as metabolically active tissues and picks it up as it flows through respiratory exchange it flows through respiratory exchange structures. structures.


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Figure 48.14


figure 48-14.jpg


Blood Transport of Respiratory Gases

• Myoglobin has a very high affinity for Myoglobin has a very high affinity for oxygen and serves as an oxygen oxygen and serves as an oxygen reserve in muscle.reserve in muscle.

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• Fetal hemoglobin has a higher affinity Fetal hemoglobin has a higher affinity for Ofor O22 than does maternal hemoglobin, than does maternal hemoglobin, allowing fetal blood to pick up Oallowing fetal blood to pick up O22 from from maternal blood in the placenta. maternal blood in the placenta.


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Figure 48.15


figure 48-15.jpg



• The affinity of hemoglobin for oxygen The affinity of hemoglobin for oxygen is decreased by the presence of is decreased by the presence of hydrogen ions or 2,3 hydrogen ions or 2,3 diphosphoglyceric acid. diphosphoglyceric acid.


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Figure 48.16


figure 48-16.jpg



• Carbon dioxide is carried in the blood Carbon dioxide is carried in the blood principally as bicarbonate ions. principally as bicarbonate ions.


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figure 48-17a.jpg




figure 48-17b.jpg


Regulating Breathing to Supply O2

• Breathing rhythm is an autonomic Breathing rhythm is an autonomic function generated by neurons in the function generated by neurons in the medulla of the brain stem and medulla of the brain stem and modulated by higher brain centers. modulated by higher brain centers.


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Figure 48.18


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• The most important feedback stimulus The most important feedback stimulus for breathing is level of COfor breathing is level of CO22 in the in the blood. blood.


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Figure 48.19


figure 48-19.jpg



• Breathing rhythm is sensitive to Breathing rhythm is sensitive to feedback from chemoreceptors on the feedback from chemoreceptors on the ventral surface of the brain stem and ventral surface of the brain stem and in the carotid and aortic bodies on the in the carotid and aortic bodies on the large vessels leaving the heart. large vessels leaving the heart.


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Figure 48.20


figure 48-20.jpg

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Chapter 48: Gas Exchange in Animals CHAPTER 48 Gas Exchange in Animals