Question

What are the three bypasses in fetal circulation?

1) Ductus arteriosus, foramen ovale, ductus venosus
2) Foramen ovale, ductus arteriosus, umbilical vein
3) Ductus venosus, umbilical vein, foramen ovale
4) Umbilical vein, ductus venosus, ductus arteriosus

Answer 1

The three bypasses in fetal circulation are the foramen ovale, ductus arteriosus, and ductus venosus, which allow blood to bypass the nonfunctional fetal lungs and liver, directing it to vital organs.

Step-by-step explanation:

The three bypasses in fetal circulation are:

1. Foramen ovale - An opening in the interatrial septum that allows blood to flow from the right atrium to the left atrium, bypassing the nonfunctional fetal lungs.
2. Ductus arteriosus - A temporary vessel connecting the pulmonary trunk to the aorta, letting blood skip the developing lungs.
3. Ductus venosus - A shunt that carries oxygenated blood from the umbilical vein, bypassing the liver, directly to the inferior vena cava and then to the heart.

The umbilical vein is not one of the bypasses, but rather the vessel through which oxygen-rich blood is delivered to the fetus from the placenta. Postnatally, changes occur in the newborn's circulation, which lead to the closure of these shunts as the baby starts breathing on its own and the lungs begin to function normally.