What is the role of surfactant in the lungs?

Surfactant plays a critical role in maintaining proper lung function primarily by reducing surface tension in the alveoli, which are the tiny air sacs where gas exchange occurs. The presence of surfactant, a mixture of lipids and proteins, prevents the alveoli from collapsing during exhalation by lowering the surface tension at the air-liquid interface. This stabilization allows the alveoli to remain open, making it easier for air to enter during inhalation and facilitating the exchange of oxygen and carbon dioxide during breathing.

By reducing surface tension, surfactant also ensures that the lungs can expand more easily, which improves overall lung compliance. This is particularly vital in the smaller alveoli where a higher surface tension could lead to collapse, also known as atelectasis. Therefore, without sufficient surfactant, individuals might experience significant breathing difficulties and reduced gas exchange efficiency.

While surfactant does indirectly support gas exchange by enhancing alveolar stability, its primary and most critical function centers on reducing surface tension.