What is the primary role of surfactant in the lungs?

Surfactant plays a crucial role in the lungs, primarily by reducing surface tension in the alveoli. The alveoli are tiny air sacs where gas exchange occurs, and they are lined with a thin film of fluid. Without surfactant, the surface tension of this fluid would cause the alveoli to collapse, especially during exhalation when the volume of air decreases.

By reducing surface tension, surfactant allows for easier expansion of the alveoli during inhalation, thus making breathing more efficient. It also helps to maintain stability in the alveoli, ensuring that they do not collapse and can remain open for gas exchange to occur effectively. This is vital for proper respiratory function and gas exchange, as it ensures that the maximum surface area is available for oxygen to enter the bloodstream and carbon dioxide to exit.

In contrast, the other roles mentioned—enhancing oxygen transport, stimulating breathing, and protecting against infections—are not the primary functions of surfactant. While surfactant does contribute to overall lung function and health, its main purpose is specifically linked to stabilizing the alveoli by reducing surface tension. This is fundamental in maintaining proper lung mechanics and ensuring effective ventilation.