What substance is secreted by alveolar cells to reduce surface tension?

Surfactant is a substance that plays a crucial role in respiratory physiology by significantly reducing surface tension within the alveoli, the tiny air sacs in the lungs where gas exchange occurs. The primary components of surfactant are lipids and proteins, which work together to create a thin film on the surface of the alveolar fluid.

By lowering surface tension, surfactant helps prevent the collapse of alveoli during exhalation, making it easier for the lungs to expand and contract. This is essential for efficient breathing and optimal gas exchange, as it ensures that the alveoli can remain open and provide adequate surface area for oxygen and carbon dioxide exchange.

While enzymes, mucus, and hormones are important in other physiological contexts, they do not have the specific role of reducing surface tension in the alveoli. Enzymes facilitate biochemical reactions, mucus traps pathogens and particles, and hormones regulate various physiological processes but do not interact with surface tension in the lungs.