Which shunt bypasses the liver in fetal circulation?

Which shunt bypasses the liver in fetal circulation?

• A. Ductus venosus
• B. Foramen ovale
• C. Ductus arteriosus
• D. Umbilical vein

Answer: (B)

In fetal life, the route that bypasses the liver is through the ductus venosus. Blood from the placenta travels in the umbilical vein and most of it is directed via the ductus venosus straight into the inferior vena cava, effectively bypassing the liver sinusoids so highly oxygenated blood reaches the heart and systemic circulation more quickly. The liver still receives some blood, but this shunt preferentially diverts flow away from the hepatic parenchyma during this stage. The other options don’t bypass the liver. The foramen ovale shunts blood from the right atrium to the left atrium to bypass the lungs. The ductus arteriosus connects the pulmonary artery to the aorta, also bypassing lung circulation. The umbilical vein is the vessel that carries placental blood to the fetus and feeds the system, not a bypass channel by itself.

In fetal life, the route that bypasses the liver is through the ductus venosus. Blood from the placenta travels in the umbilical vein and most of it is directed via the ductus venosus straight into the inferior vena cava, effectively bypassing the liver sinusoids so highly oxygenated blood reaches the heart and systemic circulation more quickly. The liver still receives some blood, but this shunt preferentially diverts flow away from the hepatic parenchyma during this stage.

The other options don’t bypass the liver. The foramen ovale shunts blood from the right atrium to the left atrium to bypass the lungs. The ductus arteriosus connects the pulmonary artery to the aorta, also bypassing lung circulation. The umbilical vein is the vessel that carries placental blood to the fetus and feeds the system, not a bypass channel by itself.