In the adult hea, floor of fossa ovalis represents:

Ans. B: Septum primumFossa ovalis and anulus ovalis lie on the atrial septum, which separates the right atrium from the left atrium.The fossa ovalis is a shallow depression, which is the site of the foramen ovale in the fetus.The anulus ovalis forms the upper margin of the fossa.The floor of the fossa represents the persistent septum primum of the hea of the embryo, and the anulus is formed from the lower edge of the septum secundum