Pulmonary alveolus

An alveolus (plural:alveoli), is an anatomical structure that has the form of a hollow cavity. In the lung, the alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood.

Matching air supply and blood supply in alveoli

For efficient gas exchange, the ratio of alveolar ventilation and capillary perfusion should be matched for each lung subunit. Ventilation of a subunit can be lowered by obstruction with fluid, particulates, mucous or tumors. Perfusion can be lowered by pulmonary embolism.

Related Topics:
Ventilation - Perfusion

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Homeostatic responses in the lungs minimize the mismatching of ventilation and blood flow. For example, alveolar epithelia secrete vasodilating substances in response to normal levels of oxygen.

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