question_answer 3)

Diffusion of gases occurs in the alveolar region only and not in the other parts of respiratory system. Why? 

Answer:

Alveoli are the primary sites of gas exchange in the respiratory system. Exchange of gases occur between blood and these tissues. O2 and CO2 are exchanged in these sites by simple diffusion mainly based on pressure/concentration gradient. The diffusion membrane for gas exchange is made up of three major layers. These layers are (i)        Squamous epithelium of alveoli. (ii)       Endothelium of alveolar capillaries; (iii)      Basement substance in between them. -Its total thickness in much less than a millimeter. Therefore, all the factors in our body are favourable for diffusion of O2 from alveoli to tissue's and that of CO2 from tissues to alveoli.