Video - Alveolar surface tension and surfactant

Alveolar surface tension is the tension that results from the forces acting on the liquid surfaces of the alveoli. The primary force acting on the liquid surface is due to the cohesive forces between neighboring water molecules.

These forces are called "hydrogen bonds" and they are responsible for water's unique properties, such as its ability to form droplets ( rain, dew, etc.). 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.