In which part of the body do oxygen and carbon dioxide exchange occur?

The exchange of oxygen and carbon dioxide occurs primarily in the alveoli, which are tiny air sacs within the lungs. These structures provide a vast surface area where the process of gas exchange takes place. When air is inhaled, it reaches the alveoli, where oxygen from the air passes into the blood capillaries surrounding them, and carbon dioxide is released from the blood into the alveoli to be exhaled. This critical exchange is facilitated by the thin walls of the alveoli and the capillaries, allowing for efficient diffusion of gases.

The bronchi serve as air passages leading to the alveoli but are not the site where exchange occurs. The lungs encompass a larger area and include various structures, but the actual exchange occurs specifically in the alveoli. Capillaries are involved in the transport of gases but function as the vessels where the gases are exchanged between the blood and the alveoli. Thus, the alveoli are the exact location where the vital exchange of gases happens in the respiratory system.