Question

(In humans) Discuss the fetal cardiovascular adaptations and their functions in fetal blood circulation.

Answer 1

The fetal circulation differs from post-natal circulation because the lungs of fetus are not in use. Blood from placenta is collected by the umbilical vein. This vein carries oxygenated blood from placenta in the fetus. One third of the blood enters the inferior vena cava through the fetal ductus venosus. The rest of the blood goes to the liver. The fetal heart has four chambers. From the liver, after passing through portal vein, blood enters the right atrium, the chamber on the upper right side of the heart. Blood from the inferior vena cava also enters the right atrium. When the blood enters the right atrium, most of it flows through the foramen ovale into the left atrium. Foramen ovale is an opening between the right and left atrium  Most of the circulation to the lower body is supplied by blood passing through the ductus arteriosus. The majority of blood flows into the left ventricle from where it is pumped through the aorta and oxygen rich blood is pumped into the body. Some of the blood moves from the aorta through the internal iliac arteries to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation.