What is the role of surfactant in the lungs?

• A. To protect the alveoli from infection
• B. To decrease surface tension and prevent alveolar collapse
• C. To facilitate gas exchange between blood and alveoli
• D. To enhance lung elasticity

Answer: (B)

Surfactant plays a critical role in the functioning of the lungs by reducing surface tension at the air-liquid interface within the alveoli. The alveoli are tiny air sacs where gas exchange occurs, and they must remain open to allow for efficient oxygen and carbon dioxide transfer. If surface tension were too high, the alveoli could collapse, especially during exhalation when the volume of air decreases.

By decreasing surface tension, surfactant helps to stabilize the alveoli and prevents them from collapsing, which is essential for maintaining proper lung function and ensuring that gas exchange can occur effectively. Surfactant is produced by type II alveolar cells and consists primarily of phospholipids and proteins, allowing it to create a thin layer that reduces tension without significantly adding weight or volume.

The incorrect options touch on other aspects of lung function but do not accurately describe the primary role of surfactant. While surfactant contributes to overall lung function and may indirectly affect factors such as lung elasticity or the immune response, its primary and essential function is to lower surface tension and prevent alveolar collapse.