The vitelline veins are developmental vessels passing between the yolk sac and the sinus venosus of the heart. There are two key vessels, the right and left vitelline veins, which pass cephalically throught the septum transversum and in close proximity to the duodenum.
Caudal to the region of the liver, the veins form anastomoses on either side of the liver. The splenic and superior mesenteric veins drain into the left vitelline vein. The distal part of the right vitelline vein regresses. One main vessel shunts blood between the left vitelline and right vitelline veins. It lies dorsal to the duodenum and is carried with it during rotation of the foregut. Ultimately, the vessel forms the distal part of the portal vein. The proximal part originates from the proximal part of the right vitelline vein.
The growing parenchyma of the liver invades the region of the veins to divide them into sinusoids. The sinusoids, extensive, enlarged vascular channels, ramify throughout the liver and anastomose with the umbilical veins.
Later within the liver, the right vitelline vein enlarges to shunt blood from the distal parts of the vitelline veins to the right side. The proximal part of the right vitelline vein forms this right hepatocardiac channel; eventually, it becomes part of the inferior vena cava. It is joined by the right and left hepatic veins which are derivatives of the proximal sections of each hepatic vein within the liver.