Foetal circulation labeled diagram with explanation shows a unique system ensuring oxygen and nutrients are delivered to the developing fetus inside the womb. The diagram of fetal circulation illustrates how oxygenated blood from the placenta enters the fetal circulation, bypassing the lungs through specialized vessels like the umbilical vein and ductus venosus. It then travels to the heart and is distributed to the fetal body.

The labeled diagram of Fetal circulation is shown below:

Labeled diagram of Fetal Circulation

What is Fetal Circulation?

Fetal circulation is a specialized system that facilitates the exchange of oxygen, nutrients, and waste products between the developing fetus and the maternal circulation during pregnancy. It operates differently from postnatal circulation due to the unique environment of the womb.

In fetal circulation, oxygenated blood is supplied to the fetus through the placenta. Maternal blood enters the placenta through the uterine arteries and exchanges oxygen and nutrients with fetal blood in the chorionic villi. Oxygenated blood from the placenta returns to the fetus through the umbilical vein, bypassing the liver via the ductus venosus to reach the inferior vena cava.

Upon reaching the fetal heart, oxygenated blood from the inferior vena cava is directed through the foramen ovale in the atrial septum, allowing it to bypass the non-functional fetal lungs and enter the left atrium. From there, it is pumped into the systemic circulation to supply oxygen and nutrients to the fetal tissues.

Deoxygenated blood returns to the placenta through the umbilical arteries, where it releases waste products and picks up oxygen for the next cycle. The ductus arteriosus shunts some blood away from the non-functional fetal lungs, directing it towards the systemic circulation.

At birth, fetal circulation undergoes significant changes to adapt to the extrauterine environment, including closure of shunts and rerouting of blood flow to accommodate lung function.

Also Read: Components of Blood

Fetal Circulation Steps

Fetal circulation involves several key steps to ensure the exchange of oxygen, nutrients, and waste products between the fetus and the placenta:

Placental Oxygenation: Oxygenated blood from the mother’s placenta enters the fetal circulation through the umbilical vein.

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Ductus Venosus Bypass: Some blood from the umbilical vein bypasses the fetal liver through the ductus venosus, joining the inferior vena cava.

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Right Atrium Entry: Oxygenated blood from the inferior vena cava enters the right atrium of the fetal heart.

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Foramen Ovale Shunt: Blood flows from the right atrium to the left atrium through the foramen ovale, bypassing the fetal lungs.

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Left Ventricle Pumping: Oxygenated blood from the left atrium is pumped into the left ventricle and then directed into the fetal systemic circulation.

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Systemic Circulation Distribution: Oxygenated blood is distributed to the fetal tissues, providing oxygen and nutrients for growth and development.

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Deoxygenated Blood Collection: Deoxygenated blood returns to the right atrium via the superior and inferior vena cava.

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Right Ventricle Pumping: Deoxygenated blood is pumped into the right ventricle and then directed to the pulmonary artery.

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Ductus Arteriosus Shunt: The ductus arteriosus shunts some blood away from the fetal lungs and into the systemic circulation.

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Umbilical Arteries Return: Deoxygenated blood is carried back to the placenta through the umbilical arteries, completing the fetal circulation loop.

Conclusion – Diagram of Fetal Circulation

Fetal circulation is a complex process essential for providing oxygen and nutrients to the developing fetus. Through specialized shunts and pathways, oxygenated blood from the placenta bypasses the non-functional fetal lungs, ensuring fetal well-being until birth when postnatal circulation takes over. Understanding fetal circulation is crucial for prenatal care and obstetric management.

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