<P> The foramen ovale ( from Latin , meaning `` oval hole '' ) forms in the late fourth week of gestation , as a small passageway between the septum secundum the ostium secundum . Initially the atria are separated from one another by the septum primum except for a small opening below the septum , the ostium primum . As the septum primum grows , the ostium primum narrows and eventually closes . Before it does so , bloodflow from the inferior vena cava wears down a portion of the septum primum , forming the ostium secundum . Some embryologists postulate that the ostium secundum may be formed through programmed cell death . </P>
where is the foramen ovale of the heart located
between the septum secundum the ostium secundum