動(dòng)物生理學(xué)5呼吸系統(tǒng)生理上(存儲(chǔ)版)
【正文】 of the body Gas Exchanges in the Lung The exchange of gases in the lung between the inspired air and the blood is governed by several important physiological mechanisms. In an ideal cardiorespiratory system, perfect equilibration between the air and the blood might be expected. This would provide optimal efficiency in gas exchange. Unfortunately , the lung is always somewhat inefficient, even in normal individuals. This inefficiency is manifested(表示 ) as a difference between alveolar Po2 and arterial Po2. With lung disease or some circulatory abnormalities, the difference can be large. Pulmonary capillary gas equilibration Under the normal circumstances, the blood spends an average of seconds in the pulmonary capillary. With a normal diffusion capacity , enough oxygen crosses the membrane to bring the red cell hemoglobin to equilibrium with the avoelar Po2 in seconds or less. Factors affecting gas exchange in the lung The thickness of alveolocapillary (respiratory) membrane surface lining (surfactant), alveolar epithelium, basement of membranes, capillary endothelium. The area of respiratory membrane about 3x108 alveoli total 70 m2, 40 m2 at resting state ( Ventilation/perfusion ratio V/Q: Gas exchange in the tissues 組織換氣的機(jī)制和影響因素與肺換氣相似，不同的是氣體的交換發(fā)生于液相，而且擴(kuò)散膜兩側(cè)的 O2和CO2分壓隨細(xì)胞代謝的強(qiáng)度和組織的血流量而異。 Al’vi?lai] (單數(shù) alveolus ), and
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