Human heart. Artwork of a healthy human heart and its associated blood vessels. The heart is supplied with blood by a network of vessels (coronary circulation) on its surface. The main vein, the vena cava (centre left, blue) carries deoxygenated blood from the body back to the heart. The main artery, the aorta (upper centre, red) carries oxygenated blood out to the body. The pulmonary artery (purple) carries blood from the heart to the lungs for gaseous exchange to occur. Oxygenated blood arrives back at the heart from the lungs through the pulmonary veins (red, either side of heart). Three arteries branch from the aorta, which supply the head and arms with blood.