The ostium secundum is a foramen in the septum primum

Septum primum

In the developing heart, the cavity of the primitive atrium becomes subdivided into right and left chambers by a septum, the septum primum, which grows downward into the cavity. The increasingly smaller gap below it is known as the ostium primum...

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It should not be confused with the foramen ovale

Foramen ovale (heart)

In the fetal heart, the foramen ovale , also ostium secundum of Born or falx septi, allows blood to enter the left atrium from the right atrium. It is one of two fetal cardiac shunts, the other being the ductus arteriosus...

, which is a foramen in the septum secundum

Septum secundum

The septum secundum, semilunar in shape, grows downward from the upper wall of the atrium immediately to the right of the primary septum and ostium secundum....

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Clinical significance

An ostium secundum that persists at large size can be a source of atrial septal defect

Atrial septal defect

Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...

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Ostium Secundum atrial septal defects are the most common atrial septal defects. This defect can arise as a result of defects of the septum primium and the septum secundum. For the septum primium, the problem can arise as a result of excess resorption of the septum during the process of apoptosis in order to form the foramen secundum. For the septum secundum, inadequate growth of it can cause atrial septal defect since it is supposed to grow and eventually overlap the foramen secundum so as to form the oval foramen.

External links

• http://www.mayoclinic.org/atrial-septal-defect/types.html
• http://sprojects.mmi.mcgill.ca/embryology/cvs/ias.html
• http://staff.um.edu.mt/acus1/Heart-b.htm