Where does gas exchange primarily occur in the respiratory system?

Gas exchange primarily occurs in the alveoli because these tiny air sacs are where oxygen and carbon dioxide are exchanged between the air in the lungs and the blood in the surrounding capillaries. The structure of alveoli facilitates this process due to their large surface area, thin walls, and extensive blood supply. This optimal design allows for efficient diffusion of gases: oxygen moves from the alveoli into the blood, and carbon dioxide moves from the blood into the alveoli to be exhaled.

While the bronchi and trachea play crucial roles in conducting air to and from the lungs, they are not involved in gas exchange directly. The larger lung structures themselves, including the bronchi and trachea, primarily function to transport air, rather than facilitate the exchange of gases at the cellular level. Thus, the alveoli are specifically specialized for the critical function of gas exchange in the respiratory system.