Prenatal narrowing or closure of the foramen ovale.
Intra-cranial pressure was reduced by release of the cerebrospinal fluid through an opening of the dura mater at the foramen magnum.
No significant intraatrial shunt were detected through the foramen ovale.
The anterior meckelian foramen is just over 10 mm in length and occurs wholly within the postsplenial.
The adductor fossa and the anterior and posterior meckelian foramina are also partially filled with matrix.
The jugular foramen is of particular importance, as it formed the exit for the internal jugular vein.
The atrial septum was intact, but was without discernible features of the oval foramen or its valve.
The circulatory changes that result in functional closure of the foramen are sudden and abrupt, occurring within the first few minutes after birth.
