smallvessel

Smallvessel refers to the small-diameter blood vessels that form the microcirculation, including arterioles, capillaries, and venules. These vessels connect larger arteries and veins and are the primary sites of blood flow regulation and metabolite exchange with tissues. The microvasculature distributes blood, contributes to local perfusion, and participates in fluid balance and inflammatory responses.

Anatomically, small vessels differ in structure. Arterioles have smooth muscle in their walls and regulate blood flow and pressure into capillary networks. Capillaries are typically the smallest vessels and consist of a single layer of endothelial cells, often with a surrounding basal lamina and supporting pericytes; they may be continuous, fenestrated, or discontinuous, reflecting tissue-specific exchange needs. Venules, which drain capillary beds, have thinner walls and larger lumens. The microcirculation is organized into networks that allow efficient gas, nutrient, and waste exchange between blood and tissues.

Physiologically, small vessels control tissue perfusion through autonomic and local regulatory mechanisms, including arteriolar vasomotion, capillary recruitment, and precapillary sphincters. Endothelial cells lining these vessels play a key role in vascular tone, barrier function, and coagulation. Inflammation can alter microvascular permeability and flow, affecting tissue homeostasis.

Clinically, small-vessel disease is a major contributor to organ dysfunction in conditions such as diabetes mellitus and hypertension. In the brain, it is associated with lacunar strokes and white matter changes; in the retina, it causes diabetic or hypertensive retinopathy; in the kidneys, microvascular damage can lead to nephrosclerosis. Diagnosis often involves imaging and functional assessment of microvascular health, while management focuses on risk factor control and addressing endothelial dysfunction.