What is the primary role of pulmonary surfactant in the respiratory system?

Pulmonary surfactant is a substance composed primarily of phospholipids and proteins that plays a critical role in maintaining normal respiratory function. Its primary function is to reduce the surface tension at the air-liquid interface within the alveoli. By lowering this surface tension, surfactant prevents alveolar collapse during exhalation and ensures that the alveoli remain open and accessible for gas exchange.

This is vital for proper lung function, as it allows for easier inflation of the lungs and maximizes the surface area available for oxygen and carbon dioxide exchange. While lubrication of alveolar walls can be a relevant aspect of how surfactant interacts with the physiology of the lungs, its more significant role is in surface tension reduction, which ultimately enhances overall respiratory efficiency.

The other options do not accurately describe the primary function of pulmonary surfactant. Surfactant does not directly enhance oxygen flow to the blood, filter particles from the air, or increase lung capacity in a direct sense—these processes are influenced by other components of the respiratory system and not solely by surfactant.