diffusion of gases only occurs in alveolar region , not in other respiratory part.why?
Alveolar surface is very thin compared to other parts of respiratory tract. The alveoli surface is surrounded by the capillaries which bring deoxygenated blood near the alveoli and take away the oxygenated blood from there after exchange of gases. So, alveoli provide the surface for exchange of gases through diffusion not other parts of respiratory tract.