Fig. 1

Diagrammatic representation of the embryological development of the PV. a The vitelline venous system arrives at the primitive liver as two paired veins (right and left), branches into the hepatic sinusoids, and then coalesce, pierce the septum tranversum (primitive diaphragm) and drain into the sinus venosus (primitive heart). These two vitelline veins communicate through three pre-hepatic anastomoses around the developing duodenum (cranial-ventral, dorsal, and caudal-ventral). b Over time, a selective involution occurs, involving the caudal part of the right vitelline vein, the cranial part of the left vitelline vein, and the caudal-ventral anastomosis. The dorsal and cranial-ventral anastomoses persist and give rise to the main PV and to the left PV, respectively. Initially, the paired umbilical veins lie more lateral than the vitelline ones, and also pierce the septum tranversum and drain into the sinus venosus. With the development of the liver, the umbilical veins fragment and connect to the hepatic sinusoids. Over time, a selective involution of the right umbilical vein and cranial portion of the left umbilical vein also occurs. c The remnant left umbilical vein cranially bifurcates, forming two new communications: one with the IVC through the ductus venosus, carrying oxygenated blood from the placenta directly to the fetus; and another with the left PV, supplying directly the liver. After birth, the ductus venosus and the left umbilical vein involute and become the ligamentum venosum and ligamentum teres, respectively