Definition: (Anatomy) A tube through which the blood circulates in the body. Blood vessels include a network of arteries, arterioles, capillaries, venules, and veins.
The arteries carry oxygenated blood away from the heart to the cells, tissues and organs. The arteries branch into arterioles, smaller arteries that carry blood to the capillaries, which are minute vessels that permeate tissues.
Blood is then carried to the venules (small veins), which join together to form veins, which return blood to the heart.