What constitutes fetal circulation?

• A. One umbilical artery and one umbilical vein
• B. Two umbilical arteries and one umbilical vein
• C. Two umbilical veins and one umbilical artery
• D. Three umbilical arteries

Answer: (B)

Fetal circulation is characterized by the presence of two umbilical arteries and one umbilical vein. In this system, the two umbilical arteries carry oxygen-poor blood from the fetus to the placenta, while the single umbilical vein brings oxygen-rich blood from the placenta back to the fetus. This arrangement is crucial because the fetus relies on the placenta for oxygenation and nutrient exchange, as its lungs are not yet functional outside the womb.

The two umbilical arteries are formed from the branches of the internal iliac arteries of the fetus, ensuring that waste products are effectively transported back to the placenta. The umbilical vein, on the other hand, delivers vital oxygenated blood, which is essential for proper fetal development. Understanding this configuration is key to recognizing how the fetus receives necessary nutrients and oxygen while removing waste, thus underpinning the critical aspects of fetal circulation.