What is the primary function of the ductus venosus?

The primary function of the ductus venosus is to shunt oxygenated placental blood away from the semi-functional liver. During fetal development, the ductus venosus connects the umbilical vein, which carries oxygen-rich blood from the placenta, directly to the inferior vena cava. This process allows the majority of this oxygenated blood to bypass the liver, which is not fully developed and functioning as it does after birth. By doing so, the ductus venosus helps ensure that the oxygen-rich blood can be delivered efficiently to the heart and subsequently to the brain and the rest of the body, maximizing the oxygen supply to the developing fetus. This unique adaptation is crucial for fetal circulation, as the liver does not need to process all the incoming blood until after birth, when it takes over metabolic and detoxification functions.