Respiration: Chapter Goals

1. Respiration: Chapter Goals After studying this chapter, students should be able to . . 1. describe the functions of the respiratory system, distinguish between the conducting and respiratory zone structures, and discuss the significance of the thoracic membranes. 2. explain how the intrapulmonary and intrapleural pressures vary during ventilation and relate these pressure changes to Boyle’s law. 3. define the terms compliance and elasticity and explain how these lung properties affect ventilation. 4. discuss the significance of surface tension in lung mechanics, explain how the law of La Place applies to lung function, and describe the role of pulmonary surfactant. 5. explain how inspiration and expiration are accomplished in unforced breathing and describe the accessory respiratory muscles used in forced breathing.

2. Respiration: Chapter Goals 6. describe the nature of asthma and emphysema. 7. explain Dalton’s law and illustrate how the partial pressure of a gas in a mixture of gases is calculated. 8. explain Henry’s law, describe how blood PO2and PCO2are measured, and discuss the clinical significance of these measurements. 9. describe the roles of the medulla oblongata, pons, and cerebral cortex in the regulation of breathing. 10. explain why the PCO2 and pH of blood, rather than its oxygen content serve as the primary stimuli in the control of breathing. 11. explain how the chemoreceptors in the medulla oblongata and the peripheral chemoreceptors in the aortic and carotid bodies respond to changes in PCO2, pH, and PO2. 12. describe the Hering, Breuer reflex and discuss its significance. 13. describe the different forms of hemoglobin and discuss the significance of these different forms.

3. Respiration: Chapter Goals 14. describe the loading and unloading reactions and explain how the extent of these reactions is influenced by the PO2 and affinity of hemoglobin for oxygen. 15. describe the oxyhemoglobin dissociation curve, discuss the significance of its shape, and demonstrate how this curve is used to derive the unloading percentage for oxygen. 16. explain how oxygen transport is influenced by changes in blood pH and temperature, and explain the effect and physiological significance of 2,3-DPG on oxygen transport. 17. list the different forms in which carbon dioxide is carried by the blood and explain the chloride shift in the tissues and the reverse chloride shift in the lungs. 18. explain how carbon dioxide affects blood pH and how hypoventilation and hyperventilation affect acid-base balance.

4. Respiration • Anatomy • Breathing • Gas Exchange • Gas Transport

5. External and Internal Respiration 13-1

6. Respiratory System Anatomy 13-2a

7. 13-2b

8. Breathing • Mechanics • Pressure and Volume Changes • Forces acting on Lungs • Regulation

9. 13-5

10. 13-6

11. 13-7

12. 13-8

13. 13-9

14. 13-10

15. 13-11

16. 13-12a

17. 13-12b

18. 13-13

19. 13-14

20. Forces Acting on Lungs • Pulling out -- Surface tension in intra-pleural space • Pulling in • Surface tension in alveoli • Elastic recoil of alveoli walls • Role of surfactants (Hyaline Membrane Disease)

21. 13-16

22. Law of LaPlace: P = 2T/r (T = surface tension; r = radius 13-17a

23. 13-17b

24. 13-18

25. Regulation of Breathing • Neural Control • Chemical Control

26. 13-33

27. Also, Hering-Breuer Reflex inhibits over-inflation of lungs 13-34

28. 13-35

29. 13-36

30. 13-37

31. 13-38

32. Gas Exchange • Pulmonary Membrane

33. 13-4

34. Dalton’s Law • Every gas in a mixture of gases exerts a partial pressure equal to the pressure it would exert if it existed alone in the same volume. • The total pressure is equal to the sum of the partial pressures. Ptotal = P1 + P2 +…..Pn

35. 13-25

36. 13-26

37. Factors Affecting Diffusion Rates • DR = DP(A)(Sol Gas)/D(sqrt MW), where • DR = Diffusion Rate • DP = Partial pressure difference across membrane • A = Area • Sol Gas = Solubility of gas • D = Distance • MW = Molecular Weight

38. Gas Transport • Oxygen • Carbon dioxide • Carbon monoxide

39. Oxygen • Methods of Transport • 1.5% dissolved in plasma • 98.5% carried by hemoglobin • Transport Kinetics • Oxygen-Hemoglobin Dissociation Curve • Bohr effect

40. 16.33a

41. 16.33b

42. 13-28

43. 13-29

44. 13-30

45. Carbon Dioxide Transport • 10% dissolved in plasma • 30% carried by hemoglobin • 60% as bicarbonate • Chloride Shift

46. Chloride Shift 13-31

47. 13-32

48. Carbon Monoxide Transport • competitive inhibitor for O2 binding - both bind to the iron of Hb

49. Chapter Summary The Respiratory System I. Alveoli are microscopic thin-walled air sacs that provide an enormous surface area for gas diffusion. A. The region of the lungs where gas exchange with the blood occurs is known as the respiratory zone. B. The trachea, bronchi, and bronchioles that deliver air to the respiratory zone comprise the conducting zone. II. The thoracic cavity is limited by the chest wall and diaphragm. A. The structures of the thoracic cavity are covered by thin, wet pleural membranes. B. The lungs are covered by a visceral pleura that is normally flush against the parietal pleura that lines the chest wall. C. The potential space between the visceral and parietal pleurae is called the intrapleural space.

50. Chapter Summary Physical Aspects of Ventilation I. The intrapleural and intrapulmonary pressures vary during ventilation. A. The intrapleural pressure is always less than the intrapulmonary pressure. B. The intrapulmonary pressure is subatmospheric during inspiration and greater than the atmospheric pressure during expiration. C. Pressure changes in the lungs are produced by variations in lung volume, in accordance with the inverse relationship between the volume and pressure of a gas described by Boyle’s law. II. The mechanics of ventilation are influenced by the physical properties of the lungs. A. The compliance of the lungs, or the ease with which they expand, refers specifically to the change in lung volume per change in transpulmonary pressure (the difference between intrapulmonary pressure and intrapleural pressure). B. The elasticity of the lungs refers to their tendency to recoil after distension. C. The surface tension of the fluid in the alveoli exerts a force directed inward, which acts to resist distension.