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

2. Chapter 48: Gas Exchange in Animals Respiratory Gas Exchange Respiratory Gas Exchange Respiratory Adaptations for Gas Exchange Respiratory Adaptations for Gas Exchange Mammalian Lungs and Gas Exchange Mammalian Lungs and Gas Exchange Blood Transport of Respiratory Gases Blood Transport of Respiratory Gases Regulating Breathing to Supply O 2 Regulating Breathing to Supply O 2

3. Chapter 48: Gas Exchange in Animals Respiratory Gas Exchange Most cells require a constant supply of O 2 and continuous removal of CO 2.Most cells require a constant supply of O 2 and continuous removal of CO 2. These respiratory gases exchange between the body fluids of an animal and its environment by diffusion.These respiratory gases exchange between the body fluids of an animal and its environment by diffusion.3

4. Chapter 48: Gas Exchange in Animals Respiratory Gas Exchange In aquatic animals, gas exchange is limited by low diffusion rate and low O 2 level in water.In aquatic animals, gas exchange is limited by low diffusion rate and low O 2 level in water. As water temperature rises, aquatic animals face a double bind in that O 2 in water decreases, butAs water temperature rises, aquatic animals face a double bind in that O 2 in water decreases, but Their metabolism and work required to move water over gas exchange surfaces increases.Their metabolism and work required to move water over gas exchange surfaces increases. Review Figure 48.2 48.2 4

5. Chapter 48: Gas Exchange in Animals Figure 48.2 figure 48-02.jpg

6. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange The evolution of large animals with high metabolic rates required adaptations to maximize respiratory gas diffusion rates:The evolution of large animals with high metabolic rates required adaptations to maximize respiratory gas diffusion rates: Increasing surface areasIncreasing 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. Review Figure 48.4 48.4 6

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8. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange Insects distribute air throughout their bodies in a system of tracheae, tracheoles, and air capillaries.Insects distribute air throughout their bodies in a system of tracheae, tracheoles, and air capillaries. Review Figure 48.5 8

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10. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange Fish have maximized gas exchange rates by having large gas exchange surface areas ventilated continuously and unidirectionally with fresh water.Fish have maximized gas exchange rates by having large gas exchange surface areas ventilated continuously and unidirectionally with fresh water. Countercurrent blood flow helps increase gas exchange efficiency.Countercurrent blood flow helps increase gas exchange efficiency. Review Figures 48.6, 48.7 48.648.748.648.710

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12. Chapter 48: Gas Exchange in Animals Figure 48.7 figure 48-07.jpg

13. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange The gas exchange system of birds includes air sacs that communicate with the lungs but are not used for gas exchange.The gas exchange system of birds includes air sacs that communicate with the lungs but are not used for gas exchange. Air flows unidirectionally through bird lungs in parabronchi.Air flows unidirectionally through bird lungs in parabronchi. Gases are exchanged in air capillaries running between parabronchi.Gases are exchanged in air capillaries running between parabronchi. Review Figures 48.8, 48.9 48.848.948.848.913

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16. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange Each breath of air remains in the bird respiratory system for two breathing cycles.Each breath of air remains in the bird respiratory system for two breathing cycles. The air sacs work as bellows to supply the air capillaries with a continuous, unidirectional flow of fresh air.The air sacs work as bellows to supply the air capillaries with a continuous, unidirectional flow of fresh air. Review Figure 48.10 48.10 16

17. Chapter 48: Gas Exchange in Animals Figure 48.10 – Part 1 figure 48-10a.jpg

18. Chapter 48: Gas Exchange in Animals Figure 48.10 – Part 2 figure 48-10b.jpg

19. Chapter 48: Gas Exchange in Animals Respiratory Adaptations for Gas Exchange Breathing in vertebrates other than birds is tidal, thus less efficient than gas exchange in fishes or birds.Breathing in vertebrates other than birds is tidal, thus less efficient than gas exchange in fishes or birds. Even though the volume of air exchanged with each breath can vary considerably, inhaled air is always mixed with stale air.Even though the volume of air exchanged with each breath can vary considerably, inhaled air is always mixed with stale air. Review Figure 48.11 48.11 19

20. Chapter 48: Gas Exchange in Animals Figure 48.11 figure 48-11.jpg

21. Chapter 48: Gas Exchange in Animals Mammalian Lungs and Gas Exchange In mammalian lungs, the gas exchange surface area provided by the millions of alveoli is enormous, andIn mammalian lungs, the gas exchange surface area provided by the millions of alveoli is enormous, and The diffusion path length between the air and perfusing blood is very short.The diffusion path length between the air and perfusing blood is very short. Review Figure 48.12 48.12 21

22. Chapter 48: Gas Exchange in Animals Figure 48.12 – Part 1 figure 48-12a.jpg

23. Chapter 48: Gas Exchange in Animals Figure 48.12 – Part 2 figure 48-12b.jpg

24. Chapter 48: Gas Exchange in Animals Mammalian Lungs and Gas Exchange Surface tension in the alveoli would make their inflation difficult if the lungs did not produce surfactant.Surface tension in the alveoli would make their inflation difficult if the lungs did not produce surfactant.24

25. Chapter 48: Gas Exchange in Animals Mammalian Lungs and Gas Exchange Inhalation occurs when contractions of the diaphragm and intercostal muscles create negative pressure in the thoracic cavity.Inhalation occurs when contractions of the diaphragm and intercostal muscles create negative pressure in the thoracic cavity. Relaxation of the diaphragm and some intercostal muscles and contraction of other intercostal muscles increases pressure in the thoracic cavity causing exhalation.Relaxation of the diaphragm and some intercostal muscles and contraction of other intercostal muscles increases pressure in the thoracic cavity causing exhalation. Review Figure 48.13 48.13 25

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27. Chapter 48: Gas Exchange in Animals Blood Transport of Respiratory Gases Oxygen is reversibly bound to hemoglobin in red blood cells.Oxygen is reversibly bound to hemoglobin in red blood cells. Each hemoglobin molecule can carry four O 2 molecules maximum.Each hemoglobin molecule can carry four O 2 molecules maximum. Because of positive cooperativity, affinity of hemoglobin for O 2 depends on the <P O 2 to which the hemoglobin is exposed.Because of positive cooperativity, affinity of hemoglobin for O 2 depends on the <P O 2 to which the hemoglobin is exposed. Therefore, hemoglobin gives up O 2 in metabolically active tissues and picks it up as it flows through respiratory exchange structures.Therefore, hemoglobin gives up O 2 in metabolically active tissues and picks it up as it flows through respiratory exchange structures. Review Figure 48.14 48.14 27

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29. Chapter 48: Gas Exchange in Animals Blood Transport of Respiratory Gases Myoglobin has a very high affinity for oxygen and serves as an oxygen reserve in muscle.Myoglobin has a very high affinity for oxygen and serves as an oxygen reserve in muscle.29

30. Chapter 48: Gas Exchange in Animals Blood Transport of Respiratory Gases Fetal hemoglobin has a higher affinity for O 2 than does maternal hemoglobin, allowing fetal blood to pick up O 2 from maternal blood in the placenta.Fetal hemoglobin has a higher affinity for O 2 than does maternal hemoglobin, allowing fetal blood to pick up O 2 from maternal blood in the placenta. Review Figure 48.15 48.15 30

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32. Chapter 48: Gas Exchange in Animals Blood Transport of Respiratory Gases The affinity of hemoglobin for oxygen is decreased by the presence of hydrogen ions or 2,3 diphosphoglyceric acid.The affinity of hemoglobin for oxygen is decreased by the presence of hydrogen ions or 2,3 diphosphoglyceric acid. Review Figure 48.16 48.16 32

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34. Chapter 48: Gas Exchange in Animals Blood Transport of Respiratory Gases Carbon dioxide is carried in the blood principally as bicarbonate ions.Carbon dioxide is carried in the blood principally as bicarbonate ions. Review Figure 48.17 48.17 34

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36. Chapter 48: Gas Exchange in Animals Figure 48.17 – Part 2 figure 48-17b.jpg

37. Chapter 48: Gas Exchange in Animals Regulating Breathing to Supply O 2 Breathing rhythm is an autonomic function generated by neurons in the medulla of the brain stem and modulated by higher brain centers.Breathing rhythm is an autonomic function generated by neurons in the medulla of the brain stem and modulated by higher brain centers. Review Figure 48.18 48.18 37

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39. Chapter 48: Gas Exchange in Animals Regulating Breathing to Supply O 2 The most important feedback stimulus for breathing is level of CO 2 in the blood.The most important feedback stimulus for breathing is level of CO 2 in the blood. Review Figure 48.19 48.19 39

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41. Chapter 48: Gas Exchange in Animals Regulating Breathing to Supply O 2 Breathing rhythm is sensitive to feedback from chemoreceptors on the ventral surface of the brain stem and in the carotid and aortic bodies on the large vessels leaving the heart.Breathing rhythm is sensitive to feedback from chemoreceptors on the ventral surface of the brain stem and in the carotid and aortic bodies on the large vessels leaving the heart. Review Figure 48.20 48.20 41

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