Updated March 12, 2015.
Definition: Alveoli
Alveoli are the tiny air sacs (only 1 cell thick) in the lungs at the end of the smallest airways, where the exchange of oxygen and carbon dioxide takes place. The average human has nearly 300 million alveoli to absorb oxygen from the air.
Learn how your lungs work:
Examples: Jim was diagnosed with bronchioalveolar carcinoma, a type of lung cancer that begins in the alveoli.