Which statement best explains the role of surfactant in gas exchange?

• A. Water within the alveoli.
• B. Surfactant-destroying organisms.
• C. Adequate amounts of surfactant.
• D. Pulmonary capillary constriction.

Answer: (C)

Gas exchange relies on keeping the alveoli open so that a large, thin surface area is available for diffusion. Surfactant is the lipoprotein coating lining the alveoli that lowers surface tension, especially in the smallest alveoli, which helps keep them from collapsing during expiration and reduces the work of breathing. When there are adequate amounts of surfactant, alveoli stay open, lung compliance is higher, and the surface area for oxygen and carbon dioxide exchange remains sufficient. If surfactant is deficient, alveoli collapse, surface area decreases, and gas exchange becomes inefficient. So, having adequate amounts of surfactant best explains its role in enabling proper gas exchange.