part_of part of part of connected to drains Homo sapiens system anterior region of body anterior vena cava http://upload.wikimedia.org/wikipedia/commons/b/b4/Venenwinkel.png The mouse has both left and right anterior vena cava. adult humans only have a right. Postnatally the left regresses and becomes non-functional (Wessels and Sedmera 2003). In the mouse, The right pulmonary vein passes dorsal to the right superior vena cava, the left pulmonary dorsal to the left superior vena cava (Biology of the Laboratory Mouse, Green). right cardiac atrium vena cava