What is the function of surfactant in the alveoli?

Surfactant plays a crucial role in the alveoli by reducing surface tension. Alveoli are tiny air sacs in the lungs where gas exchange occurs, and they are lined with a thin layer of fluid. Without surfactant, the surface tension of this fluid would be very high, making it difficult for the alveoli to expand during inhalation. This can lead to a condition known as atelectasis, where the alveoli collapse, reducing the surface area available for gas exchange.

By decreasing surface tension, surfactant ensures that the alveoli remain open at lower lung volumes, promoting stability and preventing collapse, especially during exhalation. This is particularly important because it allows for more efficient gas exchange, as open alveoli can maximize the surface area for oxygen to enter the bloodstream and carbon dioxide to be removed.

While enhancing gas exchange, promoting diffusion of oxygen, and facilitating the expulsion of carbon dioxide are vital functions in respiratory physiology, they all rely on the alveoli being properly inflated and stabilized by surfactant. Thus, the primary function of surfactant in the alveoli is to reduce surface tension and prevent alveolar collapse.