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Physiology

Physiology. Chunling Jiang MD, PhD Professor of Physiology. Respiration. Chapter 5. Introduction. Concept of Respiration : gas exchange between body and environment. This term includes three processes:

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Physiology

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  1. Physiology Chunling Jiang MD, PhD Professor of Physiology

  2. Respiration Chapter 5

  3. Introduction • Concept of Respiration : gas exchange between body and environment. This term includes three processes: 1. External respiration pulmonary ventilaion atmosphere alveoli gas exchange in lungs O2 CO2 O2 alveoli blood CO2

  4. 2. Gas transport (in blood) The blood carries O2 from the lungs to the tissues and CO2 from the tissues to the lungs 3. Internal respiration O2 blood tissue cell CO2

  5. Fig. 1 The relationship among these three processes

  6. 1. Functional Anatomy  Airways (Fig.2) 1)The nasal cavity, pharynx, trachea, bronchi, bronchiole and terminal bronchioles. 2)The airways in the lungs contain smooth muscles which are innervated by efferent autonomic nerve fibers 3) sympathetic nerve and Parasympathetic nerve

  7. ■ Innervation of respiratory tract Sympathetic n (+) NE + ß2 smooth muscles in airways relax Parasympathetic n (+) Ach + M smooth muscles in airways contract

  8. 3. Pulmonary surfactant=surface active substance  Synthesized site: Type Ⅱ alveolar cells  Composition: Dipalmitoyl phosphatidyl eholine, DPPC  Physiological Function (Fig.3) 1) to reduce the surface tension, allowing easier lung expansion 2) to alter surface tension in proportion to the volume of the alveoli . That is

  9. 3) To keep the alveoli dry. The ST tends to suck fluid into the alveolar space from the capillary. So that the reduction of the ST also prevents the transudation of fluid.

  10. 4. Motivity of pulmonary ventilation PLEURA AND INTRAPLEURAL SPACE  the visceral pleura  the parietal pleura  a potential space.

  11. 5. Intrapleural pressure(IP) ■Concept: pressure in the pleural cavity (Fig.5) ■ Measure : direct method indirect method ■ Normal value: at the end of inspiration -5 ~ -10 mmHg at the end of expiration -3 ~ -5 mmHg

  12. ■ Mechanism IP = AP - RF Intrapleural pressure = alveolar pressure - recoil force Intrapleural pressure = - recoil force

  13. Significance : 1) attracting the lung to expansion 2) accelerating venous return

  14. 6. Pressure in alveoli • Concept: pressure in alveoli inspiration-------- less than the atmospheric pressure negative expiration -------- higher than the atmospheric pressure • positive • Fig.6

  15. 7. Lung capacity and ventilation 1) Lung capacity (Fig.7) • Tidal volume (TV) • Inspiratory reserve volume (IRV) • Expiratory reserve volume (ERV) • Vital capacity (VC)

  16. 4. Vital Capacity (VC) The maximal volume of gas that can be expelled following a maximal inspiration. VC = TV + IRV + ERV Normal value: Male -------- 3.5 L Female -------- 2.5 L

  17. 5. Timed vital capacity The percentage of the vital capacity that an individual can exhale in a given duration with maximal effort. Timed vital capacity = Forced Expiratory Volume (FEV) FEV 1.0 ------- 83% FEV 2.0 ------- 96% FEV 3.0 ------- 99%

  18. 2 ) Lung ventilation 1. Pulmonary ventilation per minute 2. Alveolar ventilation per minute ■physiologic dead space anatomical dead space alveolar dead space

  19. §2 Gas Exchange  A gas diffuses from a region of high partial pressure to a region of low partial pressure. The partial pressure of a particular gas is equal to its percentage concentration times the total pressure of the gases mixture. Example PO2

  20. Partial Pressure of O2 and CO2 • Table 6-3 Pressure of O2 and CO2 in alveolar air, • venous blood, arterial blood and the tissue • P O2 (mmHg) P CO2 (mmHg) • Alveolar air 102 40 • Venous blood 40 46 • Arterial blood 100 40 • Tissue 40 46

  21. §3 Transport of oxygen and carbon dioxide 1. Transport of oxygen (1) Forms of transport O2 is carried in blood in two forms: physically dissolved ----- 0.3ml/100ml Combination with hemoglobin Hb + O2 HbO2 where Hb is deoxyhemoglobin, HbO2 is oxyhemoglobin reversibility of reaction

  22. (2) O2 content, capacity and saturation a. O2 content b. O2 capacity c. O2 saturation

  23. (3) O2 dissociation curve (Fig.9) Concept: The relation between O2 partial pressure and O2 saturation. S shaped Physiological advantages: a) PO260 ~ 100 mmHg ---- O2 combined with the Hb It makes O2 supply safe for body. b) PO2 15 ~ 60mmHg ---- HbO2 released O2 PO2  SO2 

  24. (4) Factors affecting HbO2 dissociation curve (Fig.10) Increases in PCO2, H+, T, 2,3-DPG shift the curve to the right Significance? Decreases in PCO2, H+, T, 2,3-DPG shift the curve to the left Significance?

  25. §4 Control of Ventilation • 1. Respiratory center and respiratory rhythm • Exp. • Methods of investigation---resection • ◆Respiratory center: • the upper portion of pons ----- Pneumotaxic centerThe lower pons ------ Apneustic centerMedulla ------ Medullary center • inspiratory center • expiratory center

  26. Chemical Regulation of Respiration • The respiratory control system are very sensitive to alterations in • the internal environment of the body. Changes in the body PCO2, pH • and PO2 cause changes in alveolar ventilation designed to restore • these variable to their normal values. • 1.Carbon dioxide (CO2) • The most important factor in the control of breathing under normal • conditions • Receptors: • Central chemoreceptors • 2) Peripheral chemoreceptors

  27. Experiment: PCO2  ventilation  Pathways: Mechanism: CO2 +H2O H2CO3 HCO3 + H+ H+ stimulate the chemoreceptors

  28. 2.O2 : Po2 R , ventilation Pathways: peripheral chemoreceptors 3. [H+] Pathways: central chemoreceptors peripheral chemoreceptors

  29. H+ in blood the chief site of activity is the peripheral chemoreceptors why? H+ pass across blood-brain barrier too slowly. H+ in CSF the chief site of activity is the central chemoreceptor

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