Which type of blood vessel is primarily involved in the exchange of gases?

Capillaries are the primary type of blood vessel involved in the exchange of gases. These tiny blood vessels form a network that allows for the efficient transfer of oxygen and carbon dioxide between the blood and surrounding tissues. Their walls are extremely thin, consisting of a single layer of endothelial cells, which facilitates diffusion. Oxygen from the blood can easily move into the tissues, while carbon dioxide produced by the tissues can diffuse into the blood.

Arteries are responsible for carrying oxygenated blood away from the heart to the rest of the body, and while they play a critical role in the circulatory system, they are not involved in gas exchange. Veins carry deoxygenated blood back to the heart, so their main function is not gas exchange but rather the return of blood. Arterioles are smaller branches of arteries that lead to capillaries and primarily regulate blood flow and pressure but do not engage directly in the exchange of gases. Thus, among the blood vessels listed, capillaries are uniquely structured and positioned to facilitate this vital process.