Carbon dioxide and oxygen exchange at the alveolar level occurs through which process?

The exchange of carbon dioxide and oxygen at the alveolar level occurs through diffusion, which is the movement of molecules from an area of higher concentration to an area of lower concentration. In the alveoli, oxygen is present in higher concentrations compared to the blood in the pulmonary capillaries, allowing oxygen to diffuse into the blood. Conversely, carbon dioxide is at a higher concentration in the blood than in the alveolar air, leading to its diffusion from the blood into the alveoli.

This process is crucial for respiration, as it ensures that oxygen is taken into the bloodstream while carbon dioxide is expelled from the body. Unlike filtration, which involves the passage of substances through a membrane due to pressure differences, or osmosis, which specifically refers to the movement of water across a semi-permeable membrane, diffusion is the most relevant process in the context of gas exchange in the lungs. Convection, on the other hand, pertains to fluid movement driven by differences in temperature or density, which is not applicable to this particular physiological exchange.