Functioning at the end of the circulatory cycle, the veins of the upper torso carry deoxygenated blood from the tissues of the body back to the heart to be pumped through the body again. Blood returning to the heart from the lower torso and legs enters the upper torso in a large vein called the inferior vena cava.ach pulmonary vein carries blood from a lung back to the heart where it reenters through the left atrium. Oxygenated blood exits the left ventricle of the heart and enters the aorta, the largest artery in the human body.