What is the primary function of surfactant in the lungs?

The primary function of surfactant in the lungs is to prevent alveoli from collapsing. Surfactant is a substance composed mainly of phospholipids and proteins that lines the alveoli, the tiny air sacs in the lungs where gas exchange occurs. It plays a crucial role in reducing surface tension at the air-liquid interface within the alveoli. By lowering surface tension, surfactant helps to keep the alveoli open and stable, even during exhalation, thus preventing their collapse. This is especially important since alveoli need to remain inflated to allow for efficient gas exchange of oxygen and carbon dioxide.

Without surfactant, the high surface tension could lead to alveolar collapse (a condition known as atelectasis), significantly impairing respiratory function and gas exchange. While other options may relate to the overall function of the lungs, they do not specifically capture the essential role of surfactant in maintaining alveolar stability.