umbilical vein
The umbilical vein is the conduit for blood returning from the placenta to the fetus until it involutes soon after birth.
The umbilical vein arises from multiple tributaries within the placenta and enters the umbilical cord, along with the (usually) paired umbilical arteries. Once it enters the fetus at the umbilicus, it courses upwards towards the liver in the falciform ligament and enters the liver at the porta hepatis joining with the left portal vein. Oxygenated nutrient-rich blood returning from the placenta bypasses the liver in the fetus by passing from the umbilical vein into the ductus venosus, a direct communication to the inferior vena cava.
After birth, the umbilical vein obliterates due to the changes in pressure. The remnant of the umbilical vein forms a fibrous cord, the ligamentum teres that runs in the free edge of the falciform ligament.
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