Explain the mechanism of gaseous exchange at bronchiole level.

Explanation

(1)Each bronchus divides in the lungs to form a large number of still smaller tubes called bronchioles.
(2)The smallest bronchioles have tiny air sacs at their ends.
(3)The pouch-like air sacs at the ends of the smallest bronchioles are called alveoli.
(4) The walls of the alveoli are very thin and they are surrounded by very thin blood capillaries.
(5)Since the concentration of the gases in the blood and the alveoli are not equal , there is a concentration gradient which causes the diffusion of carbon dioxide from the blood to the alveolar air and of oxygen from the alveolar air into blood .