What happens to surface tension in the alveoli when surfactant is present?

Surfactant is a substance that reduces surface tension, and it plays a crucial role in the functioning of the alveoli in the lungs. Alveoli are tiny air sacs where gas exchange occurs, and they have a thin layer of fluid on their surface. Without surfactant, the cohesive forces of the water molecules in this fluid create high surface tension, making it more difficult for the alveoli to expand and can even lead to their collapse.

When surfactant is present, it intersperses itself between the water molecules in the fluid lining the alveoli. This action disrupts the cohesive forces, thereby lowering the surface tension. As a result, the alveoli can expand more easily during inhalation, which helps to prevent them from collapsing at the end of expiration. The presence of surfactant is critical for maintaining normal lung function and ensuring efficient gas exchange. Thus, the correct response reflects the important physiological role of surfactant in maintaining lower surface tension in the alveoli, aiding in lung expansion and overall respiratory efficiency.