EMBRYOLOGY OF THE UMBILICAL VEIN

Fetal umbilical veins begin as paired structures, which join the vitelline and common cardinal veins. They all enter the sinus venosus in the 4-6 week embryo.

The liver sinusoids develop as a plexus of blood vessels within the septum transversum and communicate initially with the vitelline veins and later with the umbilical veins.

The right umbilical vein then regresses.

The left umbilical vein continues to maintain a connection between derivatives of the vitelline veins and the ductus venosus.