mikrovasculature

Mikrovasculature refers to the smallest elements of the circulatory system, including arterioles, capillaries, and venules, together with the endothelial lining and surrounding pericytes and basement membrane. This network forms the microcirculation, the principal site of exchange between blood and tissue, supporting oxygen delivery, nutrient transport, and removal of carbon dioxide and waste products. It also participates in regulating interstitial fluid balance and local blood flow.

Anatomy and cellular components: Arterioles modulate flow and pressure before capillaries. Capillaries, typically 5–10 micrometres in diameter, are lined by endothelial cells and mantled by a thin basement membrane, with pericytes closely associated in many tissues. The endothelium and its glycocalyx regulate permeability and leukocyte traffic, while pericytes contribute vascular stability and help control capillary diameter.

Physiological function: The microvasculature adjusts perfusion via vasodilation, vasoconstriction, and capillary recruitment in response to metabolic demand. Exchange occurs mainly by diffusion and transendothelial transport across capillary walls. Endothelial signaling networks, including nitric oxide and endothelins, coordinate vascular tone, while inflammatory signals can alter permeability and leukocyte trafficking.

Clinical relevance: Microvascular dysfunction is implicated in diabetes mellitus (diabetic microangiopathy), hypertension-related end-organ damage, stroke, myocardial infarction, sepsis, and aging. Structural changes such as basement membrane thickening, capillary rarefaction, and impaired endothelial function can disrupt tissue perfusion and promote edema or hypoxia.

Measurement and study: Researchers assess mikrovasculature with intravital or high-resolution imaging (capillaroscopy, confocal or two-photon microscopy) and by measuring capillary density and perfused capillary length. Biomarkers of endothelial function and angiogenesis, along with computational models, aid understanding of microvascular health and disease.