Heart, computer artwork. The heart, shown here from the front, is a hollow muscle that pumps blood around the body. The large, round chamber at lower right contains the left and right ventricles and the smaller chamber at left is the right atrium. The left atrium, at right, is barely seen. At top left is the vena cava vein, which carries deoxygenated blood into the right side of the heart. From here, the blood travels into the lungs, via the pulmonary artery (right), where it is oxygenated. The blood is then carried into the left side of the heart before travelling back into the body via the aorta at top centre, seen arching over the pulmonary artery. Branching out to the sides, behind the heart, are the lung blood vessels.