The superior vena cava is a large vein that carries oxygen-poor blood from the body into the right atrium of the heart. This vein is very short in length and may also be referred to as the precava.
Once blood from the body enters the superior and the inferior vena cavae, it is dumped into the right atrium and begins flowing throughout the heart. As the atrium contracts, the oxygen-poor blood flows into the right ventricle. Next, the ventricle contracts and pushes blood into the pulmonary artery, which delivers the blood to the lungs to become oxygenated. Next, oxygenated blood empties into the left atrium and then flows into the left ventricle. The ventricle contracts, and the blood leaves the heart through the aortic valve.