Kapillaariseinämä

Kapillaariseinämä is the Finnish term for the capillary wall, a thin endothelial layer that lines the interior of capillaries, the smallest blood vessels in the body. The wall is composed of a single layer of endothelial cells linked by tight junctions, supported by a basement membrane and, in some tracts, pericytes that help regulate blood flow and capillary permeability.

The primary function of the capillary wall is to facilitate the exchange of gases, nutrients, and waste products between the blood and the surrounding tissue. Oxygen diffuses from the blood to the interstitial fluid, while carbon dioxide and metabolic by-products move in the opposite direction. The high surface area to volume ratio and the delicate structure of the wall allow for efficient transcellular and paracellular transport.

Regulation of capillary permeability is mediated by the endothelial cells through mechanisms such as vesicular transport, junctional remodeling, and the release of vasoactive substances like nitric oxide, histamine, and VEGF. In certain tissues, the capillaries are of the continuous type, whereas in others—such as the brain, eye, and endocrine glands—they may be fenestrated or discontinuous, providing specialized permeability characteristics.

Pathological alterations of the capillary wall can result in edema, hemorrhage, or impaired delivery of oxygen and nutrients. Conditions such as diabetic microangiopathy, inflammation, and certain hemoglobinopathies target endothelial dysfunction and compromise capillary integrity, contributing to tissue damage and organ dysfunction.

Clinically, understanding the structure and regulatory mechanisms of the capillary wall informs therapeutic strategies in diseases involving microvascular complications, guiding interventions that target endothelial health and improve tissue perfusion.