Superior vena cava, inferior vena cava and pulmonary veins are all veins through which blood from the body flows into the heart. Blood from the body, after it has supplied oxygen to the body and collected carbon dioxide in return flows to the hart through superior vena cava and inferior vena cava, which are the body's two largest veins. The superior vena cava brings blood from the head and arms. The inferior vena cava carries blood from the trunk and legs. Pulmonary veins return oxygenated blood from the lungs to the heart.