What effect does surfactant have on the surface tension in the alveoli?

Surfactant plays a critical role in the respiratory system, particularly in the alveoli, which are the tiny air sacs in the lungs where gas exchange occurs. The primary function of surfactant is to reduce surface tension at the air-liquid interface within the alveoli. This reduction in surface tension is crucial for several reasons.

Firstly, by decreasing surface tension, surfactant prevents the alveoli from collapsing during exhalation. Without sufficient surfactant, the alveoli would require significantly more effort to reinflate during inhalation, leading to potential respiratory complications. Lower surface tension also helps to stabilize the alveoli, ensuring that they do not collapse or over-expand, which allows for more efficient gas exchange.

Furthermore, surfactant assists in maintaining uniform inflation of the alveoli, helping to ensure that they can all participate equally in gas exchange. This is particularly important given the varying sizes of alveoli; the Law of Laplace states that smaller alveoli would naturally have a higher pressure if surface tension were not lowered by surfactant.

In summary, surfactant decreases surface tension in the alveoli, facilitating easier breathing and enhancing the overall efficiency of the respiratory system.