interatrial foramen primum(redirected from primary interatrial foramen)
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in·ter·a·tri·al fo·ra·men pri·'mum
1. in the embryonic heart, the temporary opening between right and left atria situated between the lower margin of the septum primum and the atrioventricular canal cushions;
2. in an adult heart, the abnormal persistence of the so-named communication, which is normal in young embryos.