Gas Exchange in the Lungs
The lungs contain about 3 × 108 alveoli (little sacs) in which air and blood are brought close together so that gas exchange can occur. The principal gases exchanged are O2, which is picked up by the blood, and CO2, which leaves the blood stream and enters the air spaces of the lung. These gases need to cross the thin alveolar-capillary membrane; this crossing occurs by diffusion. In normal circumstances, the alveolar-capillary membrane presents so slight a barrier to diffusion that the blood in the alveolar capillaries achieves equilibrium with the alveolar air before leaving the capillaries.
KeywordsPartial Pressure Alveolar Ventilation Computer Solution Arterial Partial Pressure Lung Simulation
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