What is the primary function of the alveolus in the respiratory system?

The primary function of the alveolus in the respiratory system is gas exchange. Alveoli are tiny, balloon-like structures located at the end of the respiratory tree, specifically in the lungs. They have thin walls and are surrounded by a network of capillaries, which allows for efficient diffusion of gases.

When air enters the alveoli, oxygen from the inhaled air diffuses across the thin alveolar membrane into the blood in the capillaries, while carbon dioxide from the blood diffuses into the alveoli to be exhaled. This exchange is essential for maintaining the body's oxygen levels and for eliminating carbon dioxide, a waste product of cellular metabolism. The structural design of the alveoli maximizes surface area, further enhancing their capability for gas exchange.

Other functions like air filtration, mucus production, and sound production do not occur primarily within alveoli. Filtration and mucus production primarily happen in the upper respiratory tract, while sound production involves the vocal cords in the larynx, not the alveoli.