Anatomy and Physiology II Practice Test

What is the primary role of surfactant in the lungs?

1. Facilitates gas exchange

2. Traps pathogens

3. Reduces surface tension

4. Increases air pressure

The correct answer is: Reduces surface tension

Surfactant plays a crucial role in the lungs by reducing surface tension at the air-liquid interface within the alveoli, the small air sacs where gas exchange occurs. This reduction in surface tension is vital because it prevents the alveoli from collapsing during exhalation, ensuring they remain open for efficient gas exchange during inhalation. By stabilizing the alveoli, surfactant allows them to maintain their shape and increases lung compliance, making it easier for the lungs to expand with each breath. In contrast, while surfactant can indirectly facilitate gas exchange by keeping the alveoli open, its primary function is related to surface tension. Trapping pathogens is more associated with other components of the immune system, such as mucus and cilia in the respiratory tract. Increasing air pressure is not a function of surfactant but rather relates to the mechanics of breathing and the role of the diaphragm and other respiratory muscles. Therefore, the primary role of surfactant is the reduction of surface tension, making this the correct answer.