Vena sacralis, also known as the sacral vein, is a large vein that runs along the sacrum bone in the lower back and pelvis. It can refer to the medial or lateral sacral vein. There are several synonyms for the vena sacralis, including sacral venous plexus, sacral plexus, and venous sacral plexus. The sacral venous plexus is a network of veins that interconnect in the lower pelvic region. The sacral plexus is a complex web of nerves that originate from the spinal cord in the lower back. The venous sacral plexus is a complex system of veins that surrounds the sacrum bone, which can also include the coccyx bone.