Blood–air barrier

Blood–air barrier is a thin partition in the lungs where the exchange of gases takes place. It separates the blood in the pulmonary capillaries from the air in the alveoli.

Structure

The blood–air barrier is composed of the alveolar epithelium, the capillary endothelium, and their shared basement membrane. The alveolar epithelium is a single layer of squamous epithelial cells, which allows for rapid gas exchange. The capillary endothelium is also a single layer of squamous cells, and it is where the blood is separated from the air.

Function

The primary function of the blood–air barrier is to allow for the exchange of gases. Oxygen from the air in the alveoli diffuses across the barrier and into the blood in the capillaries, while carbon dioxide diffuses from the blood into the alveoli, from where it is expelled from the body during exhalation.

Clinical significance

Damage to the blood–air barrier can lead to a number of respiratory diseases, including pulmonary edema and acute respiratory distress syndrome. In these conditions, fluid leaks into the alveoli, impairing gas exchange.

See also

• Respiratory system
• Gas exchange
• Pulmonary circulation

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