During pregnancy, the fetal circulatory mechanism works in different way than ~ birth:

The fetus is linked by the umbilical cord to the placenta, the organ that develops and implants in the mother"s uterus during pregnancy.

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Through the blood vessels in the umbilical cord, the fetus receives every the essential nutrition, oxygen, and also life support from the mother through the placenta.

Waste products and also carbon dioxide native the fetus are sent back through the umbilical cord and also placenta come the mother"s circulation to it is in eliminated.


The fetal circulatory device uses two appropriate to left shunts, i beg your pardon are tiny passages that direct blood that demands to be oxygenated. The function of these shunts is to bypass certain body parts? in particular, the lungs and also liver ? that room not totally developed while the fetus is quiet in the womb. The shunts the bypass the lung are called the foramen ovale, which move blood from the ideal atrium of the love to the left atrium, and also the ductus arteriosus, which moves blood indigenous the pulmonary artery to the aorta.

Oxygen and nutrients from the mother"s blood room transferred across the placenta to the fetus. The enriched blood flows through the umbilical cord come the liver and splits into three branches. The blood climate reaches the worse vena cava, a major vein connected to the heart. Many of this blood is sent through the ductus venosus, additionally a shunt the passes extremely oxygenated blood v the liver come the worse vena cava and then to the ideal atrium the the heart. A tiny amount the this blood goes directly to the liver to give it the oxygen and also nutrients it needs.

Waste assets from the fetal blood space transferred back throughout the placenta to the mother"s blood.

Inside the fetal heart:

Blood enters the appropriate atrium, the chamber on the upper appropriate side that the heart. When the blood enters the right atrium, most of the flows v the foramen ovale into the left atrium.

Blood climate passes into the left ventricle (lower chamber of the heart) and also then come the aorta, (the big artery comes from the heart).

From the aorta, blood is sent out to the heart muscle chin in addition to the brain. After ~ circulating there, the blood returns to the appropriate atrium the the heart with the exceptional vena cava. Around two thirds the the blood will pass with the foramen ovale as defined above, but the remaining one third will pass right into the ideal ventricle, toward the lungs.

In the fetus, the placenta go the job-related of breathing instead of the lungs. As a result, just a tiny amount that the blood continues on come the lungs. Many of this blood is bypassed or shunted away from the lungs v the ductus arteriosus to the aorta. Many of the circulation come the reduced body is offered by blood passing with the ductus arteriosus.

This blood then enters the umbilical arteries and flows into the placenta. In the placenta, carbon dioxide and also waste products are released into the mother"s circulatory system, and oxygen and also nutrients indigenous the mother"s blood room released right into the fetus" blood.

At birth, the umbilical cord is clamped and the baby no longer receives oxygen and nutrients indigenous the mother. With the first breaths the life, the lungs start to expand. As the lung expand, the alveoli in the lungs room cleared that fluid. Boost in the baby"s blood pressure and a significant reduction in the pulmonary pressure reduces the need for the ductus arteriosus to shunt blood. These transforms promote the closure of the shunt. These alters increase the pressure in the left atrium of the heart, which decrease the push in the appropriate atrium. The shift in press stimulates the foramen ovale come close.

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The closure the the ductus arteriosus and also foramen ovale completes the shift of fetal circulation to newborn circulation.