In the context of respiratory physiology, what does the Law of Laplace describe?

The Law of Laplace specifically addresses the relationship between the pressure exerted by a liquid in a sphere and its radius. In the context of respiratory physiology, it is particularly relevant to the mechanics of the alveoli in the lungs. According to this law, the pressure required to keep the alveolus open is inversely proportional to its radius. This means that smaller alveoli require a higher pressure to remain inflated compared to larger ones.

This principle is critical when considering the surface tension of the fluid lining the alveoli and how it affects gas exchange. It underscores the importance of surfactant, which reduces surface tension, making it easier for smaller alveoli to inflate and ensuring uniform distribution of air across alveoli of varying sizes. Thus, the correct answer highlights the significance of alveolar radius in the mechanics of respiratory physiology, illustrating how the Law of Laplace is fundamental to understanding how alveoli function effectively during breathing.