Inferior vena cava
The inferior vena cava is also referred to as the posterior vena cava. The inferior vena cava is a large vein that carries de-oxygenated blood from the lower body to the heart. De-oxygenated blood means most of the oxygen has been removed by tissues, and therefore the blood is darker. This blood comes from the legs and the lower torso of the body. The inferior vena cava empties into the right atrium of the heart. The right atrium is located on the lower right back side of the heart. The inferior vena cava runs posterior, or behind, the abdominal cavity. This vein also runs alongside the right vertebral column of the spine. The inferior vena cava is the result of two major leg veins coming together. These leg veins are called iliac veins. The iliac veins come together at the small of the back, at the fifth lumbar vertebra. Once the iliac veins have merged, the inferior vena cava begins to transport blood to the heart.