What is the primary role of the alveoli in the lungs?

The primary role of the alveoli in the lungs is gas exchange with the bloodstream. Alveoli are tiny, balloon-like structures at the end of the bronchial tubes and are surrounded by capillaries, which are small blood vessels. When air enters the lungs, oxygen from the air passes through the thin walls of the alveoli and into the blood in the capillaries. Simultaneously, carbon dioxide, a waste product from the body, moves from the blood into the alveoli to be exhaled. This process ensures that the body receives the oxygen it needs for cellular respiration while eliminating carbon dioxide effectively.

Understanding this function is crucial, as it highlights the importance of the alveoli in respiration and overall health. The other roles mentioned in the choices, such as filtering incoming air, creating sound during speaking, and regulating body temperature, are associated with other structures and functions in the respiratory system, but they do not define the primary role of the alveoli. This distinction emphasizes the specialized function of the alveoli as the sites for gas exchange in the respiratory process.