Which physiological process is primarily responsible for the exchange of gases in the lungs?

The process primarily responsible for the exchange of gases in the lungs is diffusion. This occurs in the alveoli, which are tiny air sacs in the lungs where oxygen and carbon dioxide exchange takes place. During inhalation, oxygen enters the alveoli and higher concentrations of oxygen in the alveoli lead to its movement across the alveolar membrane into the blood, where the concentration of oxygen is lower. Conversely, carbon dioxide, which is more concentrated in the blood, diffuses into the alveoli to be exhaled.

Diffusion is a passive process that does not require energy; it relies on concentration gradients, allowing gases to move from areas of higher concentration to areas of lower concentration until equilibrium is reached. This is essential for maintaining the body's oxygen supply and removing carbon dioxide, a waste product of metabolism.

The other options, such as osmosis, filtration, and active transport, do not play the primary role in gas exchange in the lungs. Osmosis relates specifically to the movement of water through a semi-permeable membrane, filtration is a mechanical process of separating solids from fluids, and active transport involves moving substances against their concentration gradient, which is not the mechanism used during the gas exchange in this context.