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Atrial Septation

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OPENPediatrics Staff


Septum primum extends toward the endocardial cushion tissue, and a hole forms, which is termed ostium primum. This area is filled in by extension of the endocardial cushion tissue toward septum primum. Fenestration then appear at the top of septum primum, and these coalesce to form ostium secundum. 

Septum secundum then forms as an infolding of the roof of the atrial septum. Septum secundum has a concave free edge that extends beyond ostium secundum.The gap between the two septa is the foramen ovale. 

Last reviewed: June 2, 2015.

Topics: Cardiology Neonatology