What is the role of alveoli in the respiratory system?

The role of alveoli in the respiratory system is crucial for gas exchange. Alveoli are tiny, balloon-like structures located at the end of the bronchial tubes in the lungs. Their primary function is to provide a large surface area for the exchange of oxygen and carbon dioxide between the air and the bloodstream. This gas exchange occurs through a thin membrane that allows oxygen to diffuse into the blood while carbon dioxide, a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. The extensive network of alveoli ensures that a sufficient amount of oxygen can be absorbed efficiently, supporting cellular respiration and overall bodily functions.

The other roles mentioned, such as facilitating food digestion, filtering pollutants from the air, and producing mucus, are associated with other structures in the body or respiratory system. For instance, the digestive system handles food, the nose and upper respiratory tract filter air, and goblet cells in the respiratory passages produce mucus to trap debris. Therefore, alveoli specifically focus on the vital process of gas exchange.