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

The alveoli are small, balloon-like air sacs in the lungs that play a crucial role in the respiratory system. Their primary function is to facilitate the exchange of oxygen and carbon dioxide between the air we breathe and the bloodstream. When inhaling, oxygen from the air enters the alveoli and diffuses through their thin walls into the capillaries, which are tiny blood vessels surrounding them. This oxygen is then transported by red blood cells throughout the body to support cellular functions.

At the same time, carbon dioxide, which is a waste product of metabolism, diffuses from the blood back into the alveoli to be exhaled. This process of gas exchange is vital for maintaining the body’s oxygen levels and removing carbon dioxide, effectively supporting respiration and homeostasis. The other options, while related to lung functions, do not accurately describe the primary role of the alveoli, which is specifically focused on the exchange of oxygen and carbon dioxide.