Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why?
Alveoli are the tiny balloon-like structures found in the lungs and are the major site of gas exchange. The diffusion of oxygen and carbon dioxide is possible only in this particular region because these tiny structures are surrounded by the blood vessels, mainly the capillaries. The alveoli absorb the oxygen and transfer it in the surrounding capillaries with the exchange of carbon dioxide.
