View All. Arteries are the blood vessels that carry oxygenated blood away from the heart. As they move down through the arterial network, they get smaller and smaller like the branches and twigs of a tree. When they have decreased in size to a certain point, we refer to them as arterioles. Arterioles share many of the properties of arteries. They are strong, have a relatively thick wall, and contain a high percentage of smooth muscle. But they also serve another important function.