Blood circulation. Computer artwork of the blood circulation system in a human figure. The heart (red, upper centre) is a hollow muscle in the chest that pumps blood around the body. The body's main arteries (red) and veins (blue) branch out from the heart to every part of the body. The arteries carry blood away from the heart, and the veins bring blood back to the heart. With the exception of the pulmonary blood vessels, all the arteries carry oxygenated blood and all the veins carry deoxygenated blood. The oxygen is carried by red blood cells, which also carry the waste gas carbon dioxide in the deoxygenated blood.