Alveoli (plural of alveolus)

Alveoli are tiny, balloon-like structures in the lungs where the exchange of gases occurs. Their thin walls allow oxygen from the air we breathe to pass into the bloodstream and carbon dioxide from blood to be expelled when we exhale. These structures increase the surface area of the lungs significantly, making gas exchange efficient. Alveoli are surrounded by small blood vessels called capillaries that facilitate this process. Proper functioning of alveoli is essential for oxygenating the body and removing waste gases, playing a critical role in respiration and overall health.