After entering the inferior vena cava, where does blood go next in a fetus?

In a fetus, blood that enters the inferior vena cava flows into the right atrium. This flow is essential for fetal circulation, which differs from postnatal circulation due to the presence of shunts that allow blood to bypass the non-functioning fetal lungs.

Once the blood enters the right atrium, it has the option to continue into the right ventricle or pass through the foramen ovale to the left atrium. The foramen ovale is a key structure in fetal anatomy that facilitates this shunt, allowing most of the oxygen-rich blood from the placenta to bypass the non-ventilated lungs and circulate through the body. However, the immediate pathway after the inferior vena cava is to the right atrium before any shunting occurs.

This pathway is crucial for maintaining proper oxygenation and ensuring that the developing fetus can effectively exchange gases and nutrients through the placenta, allowing it to grow and develop properly before birth.