Fossa ovale
The fossa ovale (or ovalis) is the small oval depression in the interatrial septum at the site of the closed foramen ovale, which closes once fetal circulation ceases in the first few minutes of postnatal life. It represents the overlapping primary and secondary septa of the interatrial septum. It has a semilunar depression inferiorly which is the floor of the fossa, and the adjacent ridge is at the superior margin of the fossa.