Oxygenated blood travels from the placenta via the umbilical vein and most of it bypasses the liver by way of the ductus venosus. The ductus venosus links the umbilical vein to the caudal vena cava and the flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart versus the liver to be altered. | Oxygenated blood travels from the placenta via the umbilical vein and most of it bypasses the liver by way of the ductus venosus. The ductus venosus links the umbilical vein to the caudal vena cava and the flow of blood is controlled by a sphincter, enabling the proportion travelling to the heart versus the liver to be altered. |