What is the primary function of pulmonary surfactant?

The primary function of pulmonary surfactant is to lubricate the alveolar walls, which significantly affects their ability to expand and recoil during the breathing process. This surface-active substance is composed of lipids and proteins and functions to reduce surface tension at the air-liquid interface within the alveoli. By lowering surface tension, surfactant prevents the collapse of alveoli at the end of expiration, thus enhancing their stability and allowing for efficient gas exchange.

This ability to maintain alveolar stability is crucial for normal respiratory function, especially during the breathing cycle when the lungs expand and contract. If the surfactant were not present or dysfunctional, it could lead to alveolar collapse, causing serious respiratory issues like atelectasis and impaired oxygen transfer from the lungs to the bloodstream. Thus, the role of surfactant is vital for the effective operation of the respiratory system.