What facilitates the diffusion of carbon dioxide in the alveoli?

The diffusion of carbon dioxide in the alveoli is primarily driven by the concentration gradients of the gases involved. In the alveoli, there is usually a lower concentration of carbon dioxide compared to the higher concentration of carbon dioxide present in the blood returning from the body. This difference creates a concentration gradient that facilitates the movement of carbon dioxide from the blood into the alveoli, where it can then be exhaled.

When blood flows through the capillaries surrounding the alveoli, the carbon dioxide diffuses out of the blood into the alveolar spaces because it moves from an area of higher concentration (in the blood) to an area of lower concentration (in the alveoli). This process is a key aspect of gas exchange in the lungs, ensuring that carbon dioxide, a waste product of metabolism, is efficiently removed from the bloodstream.