Anatomy and Physiology II Practice Test

Surfactant plays a crucial role in the respiratory system, particularly in the lungs. Its primary function is to decrease surface tension within the alveoli, the tiny air sacs where gas exchange occurs. The alveoli are lined with a thin layer of fluid, and if surface tension were high, it would make it difficult for the alveoli to expand during inhalation and would increase the risk of collapse during exhalation—an event known as atelectasis.

By reducing surface tension, surfactant helps maintain the stability and compliance of the alveoli, allowing for easier inflation and deflation during breathing. This property is especially important in ensuring that the smaller alveoli do not collapse, as they rely on the presence of surfactant to keep the surface tension low enough to function effectively.

While surfactant does play a role in the overall function of the respiratory system, it does not primarily act to lubricate the bronchi or humidify inhaled air, nor does it increase surface tension, which would be detrimental to lung function. The production of surfactant is vital for proper respiratory mechanics, particularly in newborns, where a deficiency can lead to respiratory distress syndrome.