Answer
In the fetal heart there is an opening between the right and left atria. This hole that allows blood to flow from right atrium to left atrium directly --bypassing the right ventricle--and join the system circulation by a short-cut..
This fetal opening between right and left atria is the fossa ovale. In normal fetal development the foramen ovale closes soon after birth. This forces the poorly oxygenated right atrial blood to enter the right ventricle and be routed to the pulmonary circulation. In the lungs the blood it will pick up oxygen to be taken into the systemic circulation to supply oxygen-hungry tissues.
When the foramen ovale (oval hole) closes , what remains in that site is an oval depression --the fossa ovale.
Work Step by Step
If the foramen ovale does not close naturally, surgical intervention may be needed to close it to ensure optimal oxygenation of the blood of the baby.
