Question

Why does the exchange of gases happen only in alveoli, though arteries are present in pharynx, trachea and bronchus?

Answer 1

1. Alveoli are tiny air sacs in the lungs surrounded by capillaries 

2. They are numerous and only single cell thickness 

3. They increase the efficiency of gas exchange. 

4. Due to the difference in a gradient of O₂ oxygen diffuse from alveoli to blood capillaries.