An arteriole is a small-diameter blood vessel which forms part of the microcirculation that extends from an artery and leads to capillaries.
Capillary
Arterioles are part of the microcirculation system, along with capillaries, arteries, veins, venules, and tissue cells.
The microcirculation involves the flow of blood in the smallest blood vessels, including arterioles, capillaries, and venules.
Arterioles have muscular walls that usually consist of one or two layers of smooth muscle. They are the primary site of vascular resistance. This reduces the pressure and velocity of blood flow to enable gas and nutrient exchange to occur within the capillaries. Arterioles are innervated and also respond to various circulating hormones and other factors such as pH in order to regulate their caliber, thus modulating the amount of blood flow into the capillary network and tissues.