Why is umbilical vein oxygenated

Waste products and carbon dioxide from the fetus are sent back through the umbilical cord and placenta to the mother's circulation to be removed. Click to Enlarge. The fetal circulatory system uses 3 shunts. These are small passages that direct blood that needs to be oxygenated.

The purpose of these shunts is to bypass the lungs and liver. That's because these organs will not work fully until after birth. The shunt that bypasses the lungs is called the foramen ovale.

This shunt moves blood from the right atrium of the heart to the left atrium. The ductus arteriosus moves blood from the pulmonary artery to the aorta. Oxygen and nutrients from the mother's blood are sent across the placenta to the fetus. The enriched blood flows through the umbilical cord to the liver and splits into 3 branches.

The blood then reaches the inferior vena cava. This is a major vein connected to the heart. Most of this blood is sent through the ductus venosus. This is also a shunt that lets highly oxygenated blood bypass the liver to the inferior vena cava and then to the right atrium of the heart.

The placenta is the organ that develops and implants in the mother's womb uterus during pregnancy. The unborn baby is connected to the placenta by the umbilical cord. Waste products and carbon dioxide from the baby are sent back through the umbilical cord blood vessels and placenta to the mother's circulation to be eliminated. While still in the uterus, the baby's lungs aren't being used. Circulating blood bypasses the lungs and liver by flowing in different pathways and through special openings called shunts.

Oxygen and nutrients from the mother's blood are transferred across the placenta to the fetus through the umbilical cord. There it moves through a shunt called the ductus venosus. This allows some of the blood to go to the liver. But most of this highly oxygenated blood flows to a large vessel called the inferior vena cava and then into the right atrium of the heart. The singular umbilical vein carries oxygenated blood from the placenta to the fetus, while two umbilical arteries return deoxygenated blood to the placenta.

The three vessels coil around one another within the Wharton's jelly of the umbilical cord and enter the abdomen at the umbilicus. Inside the fetus, the vein courses alongside the falciform ligament and then to the liver 's underside. At the transverse fissure , the vein divides into two vessels, one larger than the other.

The larger of the two is joined by the portal vein , and together they enter the right lobe of the liver. The smaller vessel, now called the ductus venosus , diverges away from the liver and joins with the inferior vena cava. Within a week of birth, the infant's umbilical vein is completely obliterated and is replaced by a fibrous cord called the round ligament of the liver also called the ligamentum teres hepatis , from the Latin meaning the same.

It extends from the umbilicus to the transverse fissure, where it joins with the ligamentum venosum to separate the left and right lobes of the liver. Closure of the umbilical vein usually occurs after the umbilical arteries have closed. This prolongs the communication between the placenta and fetal heart, allowing for a sort of autotransfusion of remaining blood from the placenta to the fetus. Under extreme pressure , the round ligament may reopen to allow the passage of blood.