Final answer:
The foramen ovale is an opening in the fetal heart that allows blood to flow from the right atrium to the left atrium. It is a temporary shunt that closes after birth.
Step-by-step explanation:
The foramen ovale is an opening in the interatrial septum that allows blood to flow from the right atrium to the left atrium in the fetal heart. It is a temporary shunt that helps bypass the pulmonary circulation until the fetus starts breathing air after birth. The foramen ovale closes as the newborn begins to breathe and blood pressure in the atria increases.