THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli.

Detailed explanation-2: -According to Fick’s law of diffusion, diffusion of a gas across the alveolar membrane increases with: Increased surface area of the membrane. Increased alveolar pressure difference (PA-Pa) Increased solubility of the gas.

Detailed explanation-3: -Diffusion across this respiratory membrane proceeds very rapidly because (1) the distance is small and (2) the gases are lipid soluble. The membranes of the epithelial and endothelial cells thus do not pose a barrier to the movement of oxygen and carbon dioxide between the blood and alveolar airspaces.