What is the primary function of surfactant in the lungs?

Surfactant plays a crucial role in lung function by significantly reducing surface tension in the fluid lining the alveoli. This is essential because the alveoli are small air sacs where gas exchange occurs, and they are lined with a thin film of fluid. High surface tension in this fluid would make the alveoli collapse, especially during exhalation when the lungs are at their smallest volume.

By lowering surface tension, surfactant enables the alveoli to remain open and stabilizes them, preventing collapse and facilitating easier inflation during inhalation. This property is vital for maintaining effective gas exchange, as it allows a greater surface area for oxygen and carbon dioxide to diffuse between the air and the blood.

Other functions, such as protecting against pathogens and stimulating mucus production, are important for respiratory health, but they are not the primary function of surfactant. The main and most critical action of surfactant is to reduce surface tension, thereby aiding in mechanics of breathing and enhancing overall respiratory efficiency.