Which component of the cardiorespiratory system is involved in exchanging gases?

The alveoli are tiny air sacs located in the lungs and are the primary sites for gas exchange in the cardiorespiratory system. When air enters the alveoli, oxygen from the air diffuses across the thin walls of the alveoli into the blood in the surrounding capillaries. Simultaneously, carbon dioxide, which is a waste product of metabolism from the blood, diffuses from the blood into the alveoli to be exhaled. This crucial process allows the body to obtain oxygen, which is essential for cellular metabolism, while removing carbon dioxide.

The heart plays a vital role in pumping blood throughout the body but is not directly involved in the gas exchange process itself. Blood vessels, including arteries and veins, transport blood but do not facilitate gas exchange directly; they play a supportive role in the overall system. Capillaries, although essential for the exchange of gases at the cellular level, are not the primary site of gas exchange; that function occurs specifically at the alveolar level. Thus, the alveoli are the critical structure for gas exchange in the cardiorespiratory system, making them the correct answer.