The term ductus venosus refers to ________.

• A. A special fetal vessel that allows umbilical blood to bypass the liver
• B. An arterial structure that shunts blood to the lungs
• C. A vein that drains into the hepatic portal system
• D. A fetal structure that connects the right atrium to the left atrium

Answer: (A)

In fetal circulation, certain vessels shunt blood to prioritize delivery of oxygen to the heart and brain. The ductus venosus is a special fetal vessel that carries blood from the umbilical vein directly into the inferior vena cava, bypassing the liver. This arrangement lets well-oxygenated placental blood reach the heart quickly and efficiently. After birth, it closes and becomes the ligamentum venosum. The other structures mentioned are different shunts: one shunts blood from the arterial side toward the lungs, another drains portal blood into the liver, and another connects the right and left atria. So the description of a fetal vessel that allows umbilical blood to bypass the liver best matches the ductus venosus.