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Updated September 01, 2010

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Photo courtesy of A.D.A.M.
Definition: Alveoli are tiny, microscopic structures deep within your lungs that are bunched together in grape-like clusters to form alveolar sacs. On the surface of the alveoli are networks of tiny blood vessels called capillaries, which carry blood from the veins in other parts of the body.

It is here where carbon dioxide from the blood is exchanged for oxygen from the alveoli. After the oxygenated blood leaves the alveoli, it travels to the heart, where it is pumped out to the rest of the body. The carbon dioxide is then expelled from your body each time you exhale.

In emphysema, the walls of the alveoli are destroyed, which impairs the exchange of carbon dioxide with oxygen. This causes dyspnea and other associated symptoms of COPD.

Pronunciation: al-VEE-oh-lye
Also Known As: air sacs
Common Misspellings: alvioli, alveeoli, alveole
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