arterioláris

Arteriolar (arterioláris) refers to anything relating to arterioles, the small-diameter arteries that connect larger vessels to capillary networks. Arterioles play a central role in microcirculation and are key determinants of peripheral vascular resistance and tissue perfusion.

Structure and location: Arterioles typically range from about 10 to 100 micrometers in diameter. Their walls have a thin tunica media composed mainly of smooth muscle cells, with an endothelial lining on the interior. The adventitial layer is minimal or absent in the smallest arterioles. The rhythm and arrangement of smooth muscle give arterioles substantial regulatory capacity over blood flow.

Function and regulation: The primary function of arterioles is to regulate the amount of blood entering capillary beds in response to tissue needs. Their tone is controlled by myogenic mechanisms, autonomic nervous system input, and local chemical mediators. Vasoconstriction decreases capillary perfusion and increases systemic vascular resistance, while vasodilation enhances perfusion. Local factors such as low oxygen, high carbon dioxide, hydrogen ions, adenosine, and nitric oxide influence diameter; endothelin promotes constriction, whereas nitric oxide promotes dilation.

Clinical relevance: Changes in arteriolar structure and tone contribute to common cardiovascular conditions. Arteriolar hyperreactivity and arteriolosclerosis can raise vascular resistance, contributing to hypertension and impaired tissue perfusion. In certain settings of severe hypertension, arteriolar injury such as fibrinoid necrosis or arteriolitis may occur. Antihypertensive therapies frequently act in part by reducing arteriolar tone to lower resistance and improve organ perfusion.