Fetal Blood Circulation System

Fetal Blood Circulation System

In animals that give live birth, the fetal blood circulation is the circulatory system of a fetus. The term normally includes the entire fetoplacental circulation, which includes the umbilical cord and the blood vessels within the placenta that bring fetal blood.

The fetal (prenatal) blood circulation differs from normal postnatal circulation, primarily due to the fact that the lungs are not in use. Rather, the fetus gets oxygen and nutrients from the mother through the placenta and the umbilical cord. The introduction of breathing and the severance of the umbilical cord gives rise to numerous neuroendocrine modifications that shortly change fetal circulation into postnatal circulation.

The fetal flow of humans has been thoroughly studied by the health sciences. Much is known also of fetal blood circulation in other animals, especially animals and model organisms such as mice, by the health sciences, veterinary science, and life sciences generally.

How does the fetal circulatory system work?

During pregnancy, the unborn child (fetus) depends upon its mother for nourishment and oxygen. Given that the fetus does not breathe air, his or her blood circulates in a different way than it does after birth.

  • The placenta is the organ that establishes and implants in the mother’s womb (uterus) during pregnancy. The unborn baby is connected to the placenta by the umbilical cord.
  • All the necessary nutrition, oxygen, and life assistance from the mother’s blood go through the placenta and to the infant through the capillary in the umbilical cord.
  • Waste products and CO2 from the infant are sent back through the umbilical cord capillary and placenta to the mother’s circulation to be eliminated.

While the infant is still in the uterus, his or her lungs are not being used. The infant’s liver is not fully developed. Flowing blood bypasses the lungs and liver by flowing in various pathways and through unique openings called shunts.


The Pathway of blood flow

Blood circulation in the unborn child follows this pathway:

  • Oxygen and nutrients from the mother’s blood are moved across the placenta to the fetus through the umbilical cord.
  • This enriched blood flows through the umbilical vein towards the baby’s liver. There it moves through a shunt called the ductus venosus.
  • This allows some of the blood to go to the liver. But the majority of this highly oxygenated blood flows to a big vessel called the inferior vena cava and after that into the right atrium of the heart.
Here is what happens inside the fetal heart

When oxygenated blood from the mother gets in the ideal side of the heart it flows into the upper chamber (the right atrium). Most of the blood flows throughout to the left atrium through a shunt called the foramen ovale.

From the left atrium, blood moves down into the lower chamber of the heart (the left ventricle). It’s then pumped into the first part of the large artery originating from the heart (the ascending aorta).

From the aorta, the oxygen-rich blood is sent out to the brain and to the heart muscle itself. Blood is likewise sent to the lower body.

Blood going back to the heart from the fetal body consists of CO2 and waste products as it goes into the right atrium. It flows down into the right ventricle, where it usually would be sent to the lungs to be oxygenated. Instead, it bypasses the lungs and flows through the ductus arteriosus into the descending aorta, which links to the umbilical arteries. From there, blood recedes into the placenta. There the CO2 and waste items are released into the mother’s circulatory system. Oxygen and nutrients from the mother’s blood are moved across the placenta. Then the cycle begins once again.


Modifications at Birth

At birth, major changes occur. The umbilical cord is clamped and the baby no longer receives oxygen and nutrients from the mother. With the first breaths of air, the lungs start to expand, and the ductus arteriosus and the foramen ovale both close. The baby’s circulation and blood flow through the heart now function like an adult’s circulatory system.


The transport Molecule in Fetus

In addition to differences in circulation, the establishing fetus also uses various types of oxygen transportation particles in its hemoglobin from that when it is born and breathing its own oxygen. Fetal hemoglobin boosts the fetus’ ability to draw oxygen from the placenta.

Its oxygen-hemoglobin dissociation curve is shifted to the left, meaning that it is able to absorb oxygen at lower concentrations than adult hemoglobin. This enables fetal hemoglobin to take in oxygen from adult hemoglobin in the placenta, where the oxygen pressure is lower than at the lungs.

Till around six months old, the human baby’s hemoglobin particle is comprised of two alpha and two gamma chains (2α2γ). The gamma chains are slowly changed by beta chains up until the molecule becomes hemoglobin A with its 2 alpha and two beta chains (2α2β).