arterioolit

Arterioolit is a small branch of an artery that leads to the capillary networks of tissues. Arterioles are the principal resistance vessels in the circulatory system, playing a central role in determining mean arterial pressure and the distribution of blood flow among organs. They typically have thin walls composed of an endothelial lining and a surrounding layer of smooth muscle (the tunica media), with relatively little adventitia, which makes them highly contractile and responsive to regulatory signals.

Functionally, arterioles regulate the flow from arteries into capillaries by vasodilation and vasoconstriction. This adjustable tone controls regional perfusion to meet metabolic demands and contributes significantly to systemic vascular resistance. Autonomic nervous input, circulating hormones, and locally produced mediators influence arteriolar tone. Endothelial factors such as nitric oxide promote dilation, while endothelin promotes constriction. The myogenic response to changes in intraluminal pressure also helps stabilize capillary pressures.

Clinical relevance includes their role in hypertension and microvascular diseases. Chronic changes in arteriolar tone and structure, such as remodeling and rarefaction, can alter tissue perfusion and organ function. In the kidney, arterioles (afferent and efferent) regulate glomerular filtration rate; in the brain, autoregulation of cerebral arterioles maintains stable blood flow despite blood pressure variations.

Pharmacologically, many antihypertensive drugs target arteriolar tone. Calcium channel blockers, direct arteriolar vasodilators (e.g., hydralazine), and indirect effects through the renin–angiotensin system influence arteriolar diameter to reduce vascular resistance and blood pressure.