Class 11 NEET Biology Breathing and Exchange of Gases

(b) : In the lung, each alveolar duet opens into a blind chamber, the alveolar sac, or infundibulum. The latter consists of a central passage giving off several small pouches, the alyeoli, or air sacs on all sides.The air sacs give the infundibulum the appearance of a small bunch of grapes. The alveoli have a very thin (0.0001 mm thick ) wall composed of simple moist, nonciliated, squamous epithelium. The number of alveoli is countless and their surface area enormous. This further accelerates the gaseous exchange in the alveoli.