The hepatic segment of the inferior vena cava develops from the anastomosis between the right subcardinal vein and the right hepato-cardiac channel. The right hepato-cardiac channel (from the right omphalomesenteric vein) becomes the post-hepatic segment. The supracardinal veins collect blood from intersegmental vessels of the body wall. They give rise to the azygos and hemiazygos veins, which finally join the superior vena cava.