What is the primary function of surfactant in the lungs?

Surfactant is a complex mixture of lipids and proteins produced by the epithelial cells in the alveoli of the lungs. Its primary function is to reduce surface tension at the air-liquid interface within the alveoli. By lowering surface tension, surfactant plays a crucial role in preventing alveoli from collapsing, especially during exhalation when the lung volume is reduced. This property allows the alveoli to remain open and increases their stability, facilitating more efficient gas exchange during the respiratory cycle.

While surfactant does contribute to lung compliance, which is the measure of the lung's ability to stretch and expand, its most critical role is specifically in preventing the collapse of alveoli. This function is vital for maintaining proper lung function and effective respiration, ensuring that oxygen can efficiently enter the bloodstream and carbon dioxide can be expelled.