CAS BI 107 Lecture 6: Gas exchange
30 Oct 2018
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Document Summary
Gas exchange is the absorption and release of gases between an organism and its environment. In mammals it occurs in tiny air sacs called alveoli inside the lungs. Extremely thin adapted to carry out gas exchange. 1st layer of alveolus (epithelium), 95%type i p. Type ii pneumocytes (pulmonary) secrete a surfactant that lowers the surface tension. Film of moisture allows o2 to dissolve and diffuse, it does the same for co2. This prevents the sticky sides if the alveolus from sticking. Basic physics: particles of gas spround at in large v. Muscle contractions cause the p in the thorax to reduce below atmospheric. The reverse is true: high p small v. If gas is free to move it moves from high p to low p pressure. As a result the air is drawn into the lungs from the atm until the lung and atm p are equalized.
