Class 11 NEET Biology Breathing and Exchange of Gases

(b) In the given figure the exchange of respiratory gases occurs in alveolar cavity. The thickness of the alveolar-capillary barrier varies from 0.2 to 2.5 μm. The wall of the capillary endothelial cell is fused to that of the alveolar cell with only a very thin basement membrane between these two cells. This produces a very narrow gap across which oxygen and carbon dioxide can rapidly diffuse