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Fetal Circulation
Fetal circulation — the circulatory system of a fetus — enables gas and nutrient exchange between the developing fetus and the mother through the placenta.
Two umbilical arteries transport blood to the placenta for oxygenation, nutrient enrichment, and waste removal.
This enriched blood returns to the fetus via the umbilical vein, which splits into the hepatic portal vein and the ductus venosus.
The hepatic portal vein feeds the liver, while the ductus venosus joins the inferior vena cava, where this oxygenated blood mixes with deoxygenated blood from the lower half of the fetal body.
Simultaneously, the superior vena cava drains the upper body. Together, these vessels feed into the right atrium.
The foramen ovale directs blood from the right atrium to the left atrium, bypassing the fetal lungs. After birth, this opening closes, and blood from the right atrium gets redirected to the lungs for oxygenation.
Some blood from the right ventricle enters the pulmonary trunk but gets redirected through the ductus arteriosus to the aorta that feeds the systemic circulation.
24.38:
Fetal Circulation
Fetal circulation is a unique system that facilitates the exchange of gases, nutrients, and waste products between the developing fetus and the mother. This intricate process takes place through a special organ called the placenta.
Two umbilical arteries transport blood from the fetus to the placenta. At the placenta, the blood absorbs oxygen and nutrients while simultaneously eliminating waste products. This oxygen-enriched and nutrient-rich blood then returns to the fetus through one umbilical vein. The umbilical vein branches into two key parts: the fetal hepatic portal vein and the ductus venosus.
The hepatic portal vein serves the critical function of supplying the liver, while the ductus venosus connects to the inferior vena cava. In the inferior vena cava, the oxygenated blood mixes with deoxygenated blood from the lower half of the fetus's body.
Meanwhile, the superior vena cava collects blood from the upper body and, together with the inferior vena cava, feeds into the right atrium. The foramen ovale, a vital fetal structure, allows most of this blood to bypass the unutilized fetal lungs, moving from the right atrium directly into the left atrium and then into the aorta.
A small fraction of the blood in the right ventricle enters the pulmonary trunk. However, it is redirected through another essential structure, the ductus arteriosus, towards the aorta. The blood circulating in the aorta supplies all fetal tissues via systemic circulation. This efficient and specialized mechanism ensures the optimal growth and development of the fetus.