A degenerative string of tissue that exists in the free edge of the falciform ligament of the liver. Anatomically, the round ligament divides the left part of the liver into medial and lateral sections. The round ligament represents the remnant of the fetal left umbilical vein. The round ligament therefore only exists in mammals. Prenatally and for a month or two after birth, the left umbilical vein is patent, subsequently degenerating to fibrous tissue, the round ligament. The umbilical vein/round ligament inserts around the umbilicus and is an important landmark of the inner surface of the anterior abdominal wall[WP]. [ http://en.wikipedia.org/wiki/Round_ligament_of_liver ]