microvascular

Microvascular refers to the smallest blood vessels in the circulatory system, including arterioles, capillaries, and venules, as well as the microcirculation that links them. This network distributes blood to tissues and enables exchange of oxygen, carbon dioxide, nutrients, and waste between blood and interstitial fluid. Capillaries, with thin endothelial walls and often a surrounding basement membrane and pericytes, provide a large surface area for exchange and allow precise regulation of tissue perfusion.

Structure and regulation of the microvasculature involve endothelial cells that line the vessel lumen and release vasoactive substances such as nitric oxide and endothelin to modulate arteriolar tone. Pericytes envelop capillaries in many tissues and contribute to vessel stability and control of capillary blood flow. The microvasculature is governed by autoregulatory mechanisms, including myogenic responses, metabolic controls, and shear-stress signaling, which together match perfusion to local tissue demand.

Physiological and clinical significance center on efficient tissue oxygen delivery and metabolic health. Microvascular dysfunction, or rarefaction, occurs in conditions such as diabetes mellitus, hypertension, obesity, sepsis, and aging, and can precede or accompany macrovascular disease. Impaired endothelium-dependent dilation, increased vascular permeability, and capillary rarefaction can lead to tissue hypoxia, edema, and impaired healing.

Assessment and therapy in this area use techniques such as capillaroscopy, laser Doppler flowmetry, and capillary density imaging to evaluate microvascular structure and reactivity. In medicine and surgery, microvascular concepts underpin procedures like microvascular surgery for connecting small arteries and veins and for tissue transfer, as well as therapeutic strategies aimed at preserving or restoring microvascular perfusion.