ANATOMY

Detailed explanation-1: -Pulmonary surfactant serves several physiological roles, including (1) reducing the work of breathing by decreasing surface tension forces; (2) preventing collapse and sticking of alveoli on exhalation; and (3) stabilizing alveoli, especially those that tend to deflate at low surface tension.

Detailed explanation-2: -The surfactant lines the alveolar walls over the water film, and then reduces the surface tension and thus the collapsing pressure.

Detailed explanation-3: -It is established that pulmonary surfactant reduces surface tension at the air–water interface in the alveoli, thereby preventing collapse of these structures at end-expiration.

Detailed explanation-4: -One of the remarkable phenomena in the process of respiration is the role of the fluid coating the walls of the alveoli. This fluid, called a surfactant, lowers the surface tension of the balloon-like alveoli.

Detailed explanation-5: -By adsorbing to the air-water interface of alveoli, with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.