Alveoli are tiny air flaps in the lungs. In the alveoli, oxygen and carbon dioxide are exchanged in the blood, getting rid of the carbon dioxide and giving the oxygen to the red blood cells to be delivered to all of the muscles and organs. Alveoli are elastic, which means that they can stretch when they are filled with air.

Alveoli exchange oxygen with red blood cells when the heart’s Sinoatrial and Atrioventricular nodes send electric signals to the hearts ventricles. The right side of the heart then contracts twice, sending blood shooting into the pulmonary circulatory system, where capillary beds are located in the lungs. The Alveoli then exchange oxygen and discard carbon dioxide with the red blood cells, which then return to the heart’s left atrium.

The singular of alveoli is one alveolus. Alveoli are tiny grape-like sacs where gas exchange takes place in the lungs (oxygen and carbon dioxide). When you breathe out, the body delivers carbon dioxide to the alveoli, and you release it in your exhalation. When you breathe in, oxygen fills the alveoli and then enters the blood, so it can be delivered to the rest of the body. In asthma there is no damage to the alveoli, which is different from another common lung disease which is called: chronic obstructive pulmonary disease, in which alveoli are damaged.