The smallest arteries in the body are called arterioles. Arterioles are blood vessels that help to regulate the volume of oxygenated blood available in the capillaries that supply it to tissues and cells.
Oxygenated blood travels through the arteries as it circulates through the body. Arterioles are responsible for supplying blood to the body's major organs as well as playing a key role in regulating the blood pressure of the cardiovascular system. Through contraction and dilation, arterioles are able to increase and decrease their resistance to blood flow and control the amount of oxygenated blood being supplied to the organs.