In which part of the respiratory system does gas exchange primarily occur?

Gas exchange primarily occurs in the alveoli, which are tiny air sacs located at the end of the respiratory tree. The structure of the alveoli is designed specifically for this purpose; they have very thin walls that allow for efficient diffusion of oxygen and carbon dioxide. Each alveolus is surrounded by a network of capillaries, where the exchange of gases occurs. Oxygen from the air within the alveoli diffuses into the blood in the capillaries, while carbon dioxide, a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. This process is essential for maintaining the body's oxygen levels and removing excess carbon dioxide, making the alveoli the critical site of gas exchange in the respiratory system.