What process facilitates gas exchange between the alveoli and capillaries?

The process that facilitates gas exchange between the alveoli and capillaries is simple diffusion. This process occurs when oxygen and carbon dioxide molecules move across the alveolar and capillary membranes from areas of higher concentration to areas of lower concentration. In the alveoli, oxygen is present in higher concentrations compared to the deoxygenated blood in the surrounding capillaries. As such, oxygen moves from the alveoli into the blood. Conversely, carbon dioxide, which is more concentrated in the blood than in the alveoli, diffuses from the blood into the alveolus to be exhaled.

Simple diffusion is particularly effective in this context because it is a passive process that does not require energy; the concentration gradients of the gases drive the movement. This mechanism of gas exchange is critical for maintaining adequate oxygen levels in the bloodstream and removing waste carbon dioxide from the body efficiently.