IMMUNOLOGY

Detailed explanation-1: -Surfactant acts like a detergent by reducing alveolar surface tension, preventing collapse of alveoli during expiration and facilitating expansion during inspiration.

Detailed explanation-2: -Surface tension tends to collapse the alveoli, but this is countered by a kind of “coating” that covers the alveolar surface called surfactant. Surfactant reduces the surface tension of water, keeping the alveoli open so that we can breathe easily.

Detailed explanation-3: -Collapse of the lungs is called alectasis. Fortunately, the type II epithelial cells of the alveoli continually secrete a molecule called surfactant that solves this problem. Surfactant is a lipoprotein molecule that reduces the force of surface tension from water molecules on the lung tissue.