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. Surfactant is a complex mixture of lipids and proteins produced by the type II alveolar cells in the lungs. Its principal role is to lower the surface tension at the air-liquid interface in the alveoli, which are the tiny air sacs in the lungs where gas exchange occurs.

By reducing surface tension, surfactant prevents the alveoli from collapsing during exhalation, making it easier for them to expand and fill with air during inhalation. This action enhances lung compliance, meaning the lungs can stretch more easily, thereby improving breathing efficiency and overall respiratory function. Additionally, the presence of surfactant facilitates better gas exchange by maintaining an optimal surface area for oxygen and carbon dioxide diffusion during respiration.

While surfactant also has secondary roles, such as helping in the clearance of pathogens and debris from the lungs, its primary and most critical function is the reduction of surface tension to support effective breathing mechanics.