alveolaarkapillaarse

Alveolar capillary refers to the thin-walled capillaries that surround the alveoli in the lung. These capillaries are part of the pulmonary circulation and provide the site for gas exchange between the alveolar air and the blood. The endothelium of the alveolar capillaries is a single layer of flattened cells with intercellular gaps, allowing rapid diffusion of oxygen from alveolar air into the bloodstream and carbon dioxide from the blood into alveolar air. The surrounding alveolar epithelium consists mainly of type I pneumocytes, thin cells that share a common basal membrane with the capillary endothelium. This shared membrane constitutes the diffusion barrier, measuring only about 0.2–0.5 micrometres.

The density of alveolar capillaries is extremely high; an adult human lung contains approximately 100 to 120 thousand alveolar capillaries per milliliter of lung tissue, granting a large surface area for efficient gas exchange. Blood enters the alveolar capillaries through the pulmonary artery and is carried away by the pulmonary veins. The capillaries are embedded in a rich interstitial matrix that provides structural support and a path for biochemical signaling.

Pathological conditions can affect alveolar capillaries. In pulmonary hypertension, increased pressure in the pulmonary arteries leads to capillary remodeling and stiffening, reducing blood flow through the alveoli. In acute respiratory distress syndrome, inflammation triggers leakage of fluid from the capillaries into the alveolar space, impairing gas diffusion. Long‑term exposure to hypoxic environments can cause capillary proliferation and vascular remodeling, altering pulmonary vascular resistance.

The alveolar capillary network is essential for maintaining homeostasis of blood gases. Its thin membranes and extensive surface area allow for the rapid movement of oxygen and carbon dioxide, ensuring the respiratory and circulatory systems function in concert.