This model encompasses the entire fetoplacental circulation.
The fetal surface of the placenta is enlarged approx. 2500 times.
The model depicts how blood from the placenta is carried to the fetus by the umbilical vein. Less than a third of this enters the fetal ductus venosus and is carried to the inferior vena cava, while the rest enters the liver.
The blood then moves to the right atrium of the heart, and then most of the blood flows through the foramen ovale directly into the left atrium, thus bypassing pulmonary circulation.
The blood is then pumped through the aorta 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.
Thus, this model is useful in understanding how the fetal circulation works differently from that of born humans, mainly because the lungs are not in use. Instead, the fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord.