Corpus: Foramen ovale

The term foramen ovale cordis refers to an opening in the foetal anlage of the septum (interatrial septum) between the two atria of the heart.

The foramen ovale is a hole between the upper and lower anlage of the secondary atrial septum (septum secundum), which is closed off from the left atrium by the primary atrial septum (septum primum). It replaces the ostium secundum in the course of cardiac development.

The falx septi atriorum is found in the left atrium as a rudiment of the foramen ovale cordis.

Together with the ductus arteriosus botalli, the foramen ovale ensures that the pulmonary circulation is bypassed. Due to a pressure gradient between the right and left atrium, the blood reaches the left atrium through the flexible deformability of the septum primum.

Postnatally, the pressure of the left atrium increases with the opening of the pulmonary circulation. The septum primum attaches to the septum secundum and fuses with it to form the interatrial septum cordis. The fossa ovalis remains as a rudimentary attachment in the right wall of the atrial septum. On the side of the left atrium is the corresponding valvula foraminis ovalis, a derivative of the septum primum.

If the foramen ovale does not close or only closes inadequately, the clinical picture is that of a persistent foramen ovale.