Development of the venous system
The venous system develops from the vitelline, umbilical, and cardinal veins, which drain into the sinus venosus.
A. Vitelline Veins
- Return poorly oxygenated blood from the yolk sac.
- Right vein forms the hepatic veins and sinusoids, ductus venosus, hepatic portal, superior mesenteric, inferior mesenteric, and splenic veins and part of the IVC.
- Left vein forms the hepatic veins and sinusoids and ductus venosus.
B. Umbilical Veins
- Carry well-oxygenated blood from the placenta.
- Right vein degenerates during early development.
- Left vein forms the ligamentum teres hepatis.
C. Cardinal Veins
- Return poorly oxygenated blood from the body of the embryo.
- Anterior cardinal vein forms the internal jugular veins and SVC.
- Posterior cardinal vein forms a part of the IVC and common iliac veins.
- Subcardinal vein forms a part of the IVC, renal veins, and gonadal veins.
- Supracardinal vein forms a part of the IVC, intercostal, azygos, and hemiazygos veins.
The development of the adult venous system occurs via a complex series of shunts and involutions. Additionally, the development of the liver from the mesenchymal cells of the septum transversum imposes vascular changes in the process of forming the hepatic sinusoids.
The following figure represents the paired venous drainage into the primitive heart.
The changes in the venous system all have the common goal of introducing right-sided asymmetry in the adult system. The circulatory changes can be considered as four discrete events, shown here.
As a result of the three shunts, the right horn of the sinus venosus becomes enlarged in relation to the left side. The shunts also result in involutions and changes in certain vessels. These are shown below.