How is gas exchange brought about at the alveoli?
Gaseous exchange in the alveoli: The uptake of O2 and release of CO2by the blood of the alveolar capillaries is by diffusion, when the gases pass from the regions of high pressure to those of low pressure. The partial pressure of 02 in the blood of the alveolar capillaries is considerably lower (40mm of Hg). The oxygen diffuses into the capillaries; its O2 pressure has been raised to about 100mm of Hg, the same as alvelolar O2. In the similar manner diffusion of CO2 out of the blood takes place.