ANATOMY

Detailed explanation-1: -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-2: -When you inhale, your diaphragm contracts. This creates negative pressure in your chest, causing the alveoli to expand and pull in air. When you exhale, your diaphragm relaxes.

Detailed explanation-3: -Surfactant is released from the lung cells and spreads across the tissue that surrounds alveoli. This substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy.

Detailed explanation-4: -By lowering and varying surface tension as a function of alveolar size (radius), lung surfactant makes equilibrium pressures more equal in different sized alveoli. As a result, small airsacs resist collapse during expiration, and large alveoli do not over-inflate during inspiration.