What role does pulmonary fluid play in the respiratory system?

Pulmonary fluid plays a crucial role in preventing the collapse of alveoli, which are the tiny air sacs in the lungs where gas exchange occurs. This fluid, found in the interstitial spaces and within the alveoli themselves, helps maintain surface tension and keeps the alveoli inflated. By reducing surface tension, pulmonary fluid prevents the alveoli from collapsing during exhalation, ensuring that they remain open and ready for gas exchange during inhalation. This is vital for effective respiration, as collapsed alveoli can hinder oxygen uptake and carbon dioxide removal, leading to impaired respiratory function.

While the other options relate to various functions in the body, they do not accurately reflect the primary role of pulmonary fluid in the respiratory system. For instance, although gas diffusion is critical, it is more about the structural integrity provided by alveoli rather than fluid absorption or temperature regulation.