Path

They run upward at first in front, and subsequently on either side of the intestinal canal.

They unite on the ventral aspect of the canal, and beyond this are connected to one another by two anastomotic branches, one on the dorsal, and the other on the ventral aspect of the duodenal portion of the intestine

Intestine

In human anatomy, the intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine...

, which is thus encircled by two venous rings; into the middle or dorsal anastomosis the superior mesenteric vein

Superior mesenteric vein

In anatomy, the superior mesenteric vein is a blood vessel that drains blood from the small intestine . At its termination behind the neck of the pancreas, the SMV combines with the splenic vein to form the hepatic portal vein...

 opens.

The portions of the veins above the upper ring become interrupted by the developing liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 and broken up by it into a plexus of small capillary-like vessels termed sinusoids.

Derivatives

The vitelline veins give rise to

• Hepatic veins
• Inferior portion of Inferior vena cava
  Inferior vena cava
  The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
  
  
• Portal vein
• Superior mesenteric vein
  Superior mesenteric vein
  In anatomy, the superior mesenteric vein is a blood vessel that drains blood from the small intestine . At its termination behind the neck of the pancreas, the SMV combines with the splenic vein to form the hepatic portal vein...
  
  

The branches conveying the blood to the plexus are named the venae advehentes, and become the branches of the portal vein. The vessels draining the plexus into the sinus venosus are termed the venae revehentes, and form the future hepatic veins. Ultimately the left vena revehens no longer communicates directly with the sinus venosus, but opens into the right vena revehens. The persistent part of the upper venous ring, above the opening of the superior mesenteric vein, forms the trunk of the portal vein.