Alternative definition : NCI-GLOSS: Tiny air sacs at the end of the bronchioles (tiny branches of air tubes)
in the lungs. The alveoli are where the lungs and the bloodstream exchange carbon
dioxide and oxygen. Carbon dioxide in the blood passes into the lungs through the
alveoli. Oxygen in the lungs passes through the alveoli into the blood.; CDISC: Any of the terminal sacs in the lungs through which gas exchange takes place
with the pulmonary capillary blood.;