The shunt that bypasses the lungs is called the foramen ovale. This shunt moves blood from the right atrium of the heart to the left atrium. The ductus arteriosus moves blood from the pulmonary artery to the aorta. Oxygen and nutrients from the mother's blood are sent across the placenta to the fetus.

What is the function of the foramen ovale in the fetal heart?

Before birth, the foramen ovale allows blood flow to bypass the lungs (a fetus gets the oxygen it needs from the placenta, not the lungs). That way, the heart doesn't work hard to pump blood where it isn't needed. When newborns take their first breath, a new flow direction happens.

How does blood flow through the foramen ovale?

When oxygenated blood from the mother enters the right side of the heart, it flows into the upper chamber (the right atrium). Most of the blood flows across to the left atrium through a shunt called the foramen ovale. From the left atrium, blood moves down into the lower chamber of the heart (the left ventricle).