The pulmonary alveoli are small sacs found in the lungs, where gas exchange takes places.
Some of their features are:
• They are found in the respiratory bronchioles.
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• They are cup-shaped cavities
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• The gas exchange happens by diffusion in the alveolar membrane.
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• They consist of an epithelial layer and an extracellular matrix surrounded by capillaries.
• They are found only in mammalian lungs
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• They can stretch during inhalation thanks to collagen fibers.
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• In humans, they are functional at 32 weeks of gestation, but they continue to develop until puberty.