Where does gas exchange primarily occur in the respiratory system?

Gas exchange primarily occurs in the alveoli, which are small air sacs located in the lungs. The alveoli provide a vast surface area, significantly increasing the efficiency of gas exchange. Their thin walls enable oxygen from the inhaled air to diffuse easily through the alveolar membrane into the capillaries, where it enters the bloodstream. At the same time, carbon dioxide from the blood diffuses into the alveoli to be exhaled.

The bronchi and trachea are parts of the airway that serve primarily as passageways for air to travel to and from the lungs but do not participate in gas exchange. The lungs encompass the alveoli, but they are not the site of gas exchange activity themselves; it is the alveolar sacs within the lungs that perform this critical function. Thus, alveoli are specifically adapted for the tasks of oxygen uptake and carbon dioxide release, making them the primary site of gas exchange in the respiratory system.