Tags: Anatomical Structure.
The limbus of fossa ovalis (anulus ovalis) is the prominent oval margin of the fossa ovalis. It is in the right atrium.It is most distinct above and at the sides of the fossa; below it is deficient. A small slit-like valvular opening is occasionally found at the upper margin of the fossa leading upward beneath the limbus into the left atrium; it is the remains of the fetal aperture (foramen ovale) between the two atria.
