What is the primary role of surfactant in the alveoli?

Surfactant plays a critical role in the alveoli by reducing surface tension. The alveoli are small air sacs in the lungs where gas exchange occurs, and they are lined with a thin layer of fluid. If surface tension in this fluid is too high, the alveoli can collapse, making it much more difficult to inflate them during breathing. Surfactant, a mixture of lipids and proteins secreted by type II alveolar cells, lowers the surface tension at the air-liquid interface, thus stabilizing the alveoli and ensuring they remain open and can expand easily during inhalation. This function is vital for efficient gas exchange and to prevent respiratory distress, allowing for proper lung function and maintaining adequate oxygen levels in the blood.