Diffusion of oxygen occurs in the alveolar region only and not in other parts of respiratory system. How do you justify the statement ?

Explanation

Alveoli are primary sites of exchange of gas by simple diffusion. Aleveolar region is having enough pressure gradient to facilitate diffusion of gases. Other regions of the respiratory system doesn.t have the required pressure gradient.
High `pO_2`, low `pCO_2`, lesser `H^+` concentration, low temperature conditions in alveoli favourable for diffusion of `O_2` and formation of oxyhaemoglobin. Solubility of gases as well as thickness of the membrane are also some of the important factors that can effect the ratio of diffusion.