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About this Chapter

Explore the dynamics of gas exchange, diffusion, and solubility in the respiratory system. Understand the transport of oxygen and carbon dioxide in the blood, including the role of hemoglobin. Dive into cellular respiration and the regulation of ventilation.

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About this Chapter

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  1. About this Chapter • Diffusion and solubility of gases • Gas exchange in lungs and tissues • Gas transport in the blood • Regulation of ventilation

  2. Overview O2 CO2 Airways Alveoli of lungs O2 CO2 6 CO2 exchange at alveolar-capillary interface Oxygen exchange at alveolar-capillary interface 1 O2 CO2 Pulmonary circulation Oxygen transport 2 5 CO2 transport Systemic circulation CO2 O2 4 CO2 exchange at cells Oxygen exchange at cells 3 CO2 O2 Cellular respiration Cells Nutrients ATP Overview of oxygen and carbon dioxide exchange and transport Figure 18-1

  3. Diffusion and Solubility Diffusion Rate : Surface area x Concentration Gradient x Membrane Permeability Membrane Thickness • Surface area • Constant • Concentration gradient • Most important factor • Membrane thickness • Constant • Diffusion distance • Constant • Thus, Diffusion Rate is proportional to Concentration Gradient

  4. Movement of Gases • Pressure gradient • Solubility of gas in liquid • Temperature (in body, relatively constant)

  5. Behavior of Gases in Solution (a) Initial state: no O2 in solution (b) Oxygen dissolves. (c) At equilibrium, PO2 in air and water is equal. Low O2 solubility means concentrations are not equal. PO2 = 100 mm Hg PO2 = 100 mm Hg [O2] = 5.20 mmol/L PO2 = 100 mm Hg PO2 = 0 mm Hg [O2] = 0.15 mmol/L Figure 18-2a–c

  6. Behavior of Gases in Solution (a) Initial state: no O2 in solution PO2 = 100 mm Hg PO2 = 0 mm Hg Figure 18-2a–c (1 of 3)

  7. Behavior of Gases in Solution (a) Initial state: no O2 in solution (b) Oxygen dissolves. PO2 = 100 mm Hg PO2 = 0 mm Hg Figure 18-2a–c (2 of 3)

  8. Behavior of Gases in Solution (a) Initial state: no O2 in solution (b) Oxygen dissolves. (c) At equilibrium, PO2 in air and water is equal. Low O2 solubility means concentrations are not equal. PO2 = 100 mm Hg PO2 = 100 mm Hg [O2] = 5.20 mmol/L PO2 = 100 mm Hg PO2 = 0 mm Hg [O2] = 0.15 mmol/L Figure 18-2a–c (3 of 3)

  9. Behavior of Gases in Solution Figure 18-2c–d

  10. Gas Exchange at the Alveoli and Cells PLAY Animation: Respiratory System: Gas Exchange Figure 18-3

  11. Partial Pressures

  12. Gas Exchange

  13. Causes of Low Alveolar PO2 • Inspired air has abnormally low oxygen content • Altitude • Alveolar ventilation is inadequate • Decreased lung compliance • Increased airway resistance • Overdose of drugs

  14. Alveolar Ventilation Pathological conditions that reduce alveolar ventilation and gas exchange Figure 18-4a

  15. Alveolar Ventilation Figure 18-4b

  16. Alveolar Ventilation Figure 18-4c

  17. Alveolar Ventilation Figure 18-4d

  18. Alveolar Ventilation Figure 18-4e

  19. Gas Exchange Oxygen diffuses across alveolar epithelial cells and capillary endothelial cells to enter the plasma Figure 18-5

  20. Gas Exchange • Pathological changes • Decrease in amount of alveolar surface area • Increase in thickness of alveolar membrane • Increase in diffusion distance between alveoli and blood

  21. Oxygen Transport ARTERIAL BLOOD Capillary endothelium O2 dissolved in plasma (~ PO2) < 2% O2 O2 + Hb Hb•O2 > 98% Red blood cell Alveolus Alveolar membrane Transport to cells Cells Hb + O2 Hb•O2 O2 Used in cellular respiration O2 dissolved in plasma Summary of oxygen transport in the blood Figure 18-6

  22. Oxygen Transport The role of hemoglobin in oxygen transport Figure 18-7a

  23. Oxygen Transport Figure 18-7b

  24. Oxygen Transport Figure 18-7c

  25. The Hemoglobin Molecule The amount of oxygen bound to hemoglobin depends on the PO2 of plasma Figure 18-8

  26. Oxygen-Hemoglobin Dissociation Curve Figure 18-9

  27. Oxygen Binding Physical factors alter hemoglobin’s affinity for oxygen Figure 18-10a

  28. Oxygen Binding Figure 18-10b

  29. Oxygen Binding Figure 18-10c

  30. 2,3-diphosphoglycerate (intermediate in glycolysis pathway) lowers Hb binding affinity 2,3-DPG alters hemoglobin’s affinity for oxygen Figure 18-11

  31. Oxygen Binding Differences in oxygen-binding properties of maternal and fetal hemoglobin Figure 18-12

  32. Oxygen Binding Factors contributing to the total oxygen content of arterial blood Figure 18-13

  33. Carbon Dioxide Transport • Dissolved: 7% • Converted to bicarbonate ion in rbc: 70% • Bound to hemoglobin: 23% • Hemoglobin also binds H+, • Hb and CO2: carbaminohemoglobin

  34. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Cl– Alveoli CA H2O + CO2 HCO3– H2CO3 HCO3– in plasma Hb•H H+ + Hb Figure 18-14

  35. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Cellular respiration in peripheral tissues Capillary endothelium Cell membrane Alveoli Figure 18-14 (1 of 17)

  36. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Capillary endothelium Cell membrane Alveoli Figure 18-14 (2 of 17)

  37. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 Capillary endothelium Cell membrane Alveoli Figure 18-14 (3 of 17)

  38. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Capillary endothelium Cell membrane Alveoli Figure 18-14 (4 of 17)

  39. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) CA CO2 + H2O H2CO3 Capillary endothelium Cell membrane Alveoli Figure 18-14 (5 of 17)

  40. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) HCO3– CA CO2 + H2O H2CO3 H+ + Hb Capillary endothelium Cell membrane Alveoli Figure 18-14 (6 of 17)

  41. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) HCO3– CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Alveoli Figure 18-14 (7 of 17)

  42. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Alveoli Figure 18-14 (8 of 17)

  43. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Alveoli Figure 18-14 (9 of 17)

  44. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Alveoli Figure 18-14 (10 of 17)

  45. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Alveoli Figure 18-14 (11 of 17)

  46. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Alveoli Figure 18-14 (12 of 17)

  47. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Cl– Alveoli HCO3– HCO3– in plasma Figure 18-14 (13 of 17)

  48. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Cl– Alveoli HCO3– HCO3– in plasma Hb•H H+ + Hb Figure 18-14 (14 of 17)

  49. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Cl– Alveoli HCO3– H2CO3 HCO3– in plasma Hb•H H+ + Hb Figure 18-14 (15 of 17)

  50. Carbon Dioxide Transport in the Blood VENOUS BLOOD CO2 Dissolved CO2 (7%) Cellular respiration in peripheral tissues Red blood cell CO2 + Hb Hb•CO2 (23%) Cl– HCO3– HCO3– in plasma (70%) CA CO2 + H2O H2CO3 H+ + Hb Hb•H Capillary endothelium Cell membrane Transport to lungs Dissolved CO2 Dissolved CO2 CO2 Hb + CO2 Hb•CO2 Cl– Alveoli CA H2O + CO2 HCO3– H2CO3 HCO3– in plasma Hb•H H+ + Hb Figure 18-14 (16 of 17)

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