What is the primary function of the alveoli?

The primary function of the alveoli is to facilitate gas exchange. These tiny, balloon-like structures are located in the lungs and are where oxygen and carbon dioxide are exchanged between the air we breathe and the blood. When air enters the alveoli, oxygen diffuses through the thin walls of the alveoli into the surrounding capillaries, where it binds to hemoglobin in red blood cells. Simultaneously, carbon dioxide, which is a waste product of metabolism, moves from the blood into the alveoli to be exhaled out of the body. This process is essential for maintaining the body's oxygen supply and removing carbon dioxide, which is crucial for respiratory health and overall homeostasis.

The other options don't align with the primary functions of the respiratory system. Supporting the tongue, sealing off the windpipe, or connecting ribs during breathing do not pertain to the alveoli's role in respiration. Instead, they involve other anatomical structures and functions unrelated to gas exchange.