What are alveoli?
It is called the alveoli. Gray's Anatomy (1918) describes it as tiny air sacs at the end of the smallest airways.
What it is
- Tiny air sacs at the end of the smallest airways.
- About 300 million in each pair of lungs.
- The site where oxygen enters the blood and carbon dioxide leaves it.
Where it is
- Grouped in clusters at the ends of the bronchioles.
- Each surrounded by a network of pulmonary capillaries.
- Their walls are only one cell thick.
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Last verified: 2026-07-18
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