Beating heart. The heart is a hollow muscular organ that pumps blood to the lungs and then around the body. Deoxygenated blood travels to the lungs through the branched pulmonary arteries either side of the heart, and is returned to the lungs through pulmonary veins. It is then pumped to the rest of the body through the arched aorta top, oxygenating body tissues before returning to the heart through the vena cava down left at start. Coronary arteries red on the heart supply the heart muscle itself with oxygen.