Human heart. Computer artwork of a healthy human heart, seen in external view. Main blood vessels that service the heart are visible at top, with smaller coronary arteries seen branching across the ventricular surface. As a pump the heart circulates blood around the body. It consists of four chambers: chambers on the left side (at right on image) receive oxygenated blood from the lungs and pump it to the body via the aortic arch artery (top centre). Used blood drained from the body is pumped through the right side of the heart to the lungs, through branched pulmonary arteries (below the aortic arch). Special mechanisms in the heart maintain its cardiac pump-rhythm.