What is the primary function of surfactant in the lungs?

The primary function of surfactant in the lungs is to reduce surface tension in the alveoli, preventing collapse. Surfactant is a complex mixture of lipids and proteins produced by the type II alveolar cells in the lungs. Its unique molecular structure allows it to intersperse among the fluid lining the alveoli, decreasing the cohesive forces between water molecules. This reduction in surface tension is crucial because it helps stabilize the alveoli during the respiratory cycle. If surface tension were not reduced, the alveoli could collapse, making it significantly more difficult for the lungs to expand and function effectively during breathing.

The presence of surfactant also facilitates the maintenance of alveolar integrity, particularly at low lung volumes, thereby contributing to the overall efficiency of lungs in gas exchange. While surfactant can contribute indirectly to other processes in the lungs, such as improving lung compliance and decreasing the work of breathing, its primary role remains the reduction of surface tension to prevent alveolar collapse.