foramen ovale is located where on the fetal heart
Foramen ovale (heart) 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.[4]