What is the role of the alveoli in the respiratory system?

The primary role of the alveoli in the respiratory system is gas exchange. These tiny, balloon-like structures are located at the ends of the bronchioles in the lungs and are crucial for the respiratory process. The alveoli are surrounded by a dense network of capillaries, which are small blood vessels. When air is inhaled, oxygen from the air passes through the thin walls of the alveoli and into the blood in the capillaries. At the same time, carbon dioxide—a waste product generated by the body's metabolism—moves from the blood into the alveoli. This two-way exchange allows oxygen to enter the bloodstream for transport to cells throughout the body while facilitating the removal of carbon dioxide, which is then exhaled.

Though the other options mention concepts related to breath and respiration, they do not accurately capture the primary function of the alveoli. Oxygen storage is not a function of the alveoli since they do not store oxygen but facilitate its transfer. Carbon dioxide production does not occur in the alveoli; instead, it is a result of cellular metabolism within the body's tissues. Additionally, air filtration primarily occurs in the upper respiratory tract, where larger particles are trapped before reaching the alveoli. Therefore, the unique structure and function