What is the function of surfactant in the alveoli?

• A. It aids in gas exchange
• B. It reduces surface tension
• C. It enhances air filtration
• D. It prevents airway obstructions

Answer: (B)

Surfactant plays a crucial role in maintaining the stability of the alveoli, which are the tiny air sacs in the lungs where gas exchange occurs. One of the most important functions of surfactant is to reduce the surface tension of the fluid lining the alveoli. This reduction in surface tension is vital for preventing the alveoli from collapsing, particularly during exhalation when the lung volume decreases. By minimizing the surface tension, surfactant ensures that the alveoli remain open and can expand easily during inhalation, thus facilitating efficient gas exchange of oxygen and carbon dioxide.

In addition, surfactant also helps to distribute the surface tension evenly across the alveoli, which prevents uneven filling and potential collapse of smaller alveoli while allowing for proper lung function. Although gas exchange does occur in the alveoli, the primary mechanism for enhancing it is the increased surface area and improved compliance provided by the presence of surfactant, rather than the surfactant itself directly aiding in the gas exchange process.