part of part of anatomical conduit atrial septum primum foramen secundum UBERON:0006678 FMA:71105 SCTID:308854001 UMLS:C1517293 NCIT:C34179 EHDAA2:0001828 The foramen secundum is an opening in the septum primum, a precursor to the interatrial septum of the human heart. It is formed at a later developmental stage than the foramen primum. Its location is also different relative to the site of the foramen primum in the septum primum. Second of the two openings to perforate the septum primum between the two atria of the embryonic heart. [TFD][VHOG] The tetrapod clade develops a complete atrial septum and loses the fifth aortic arch altogether. [ISBN:978-0030223693 Liem KF, Bemis WE, Walker WF, Grande L, Functional Anatomy of the Vertebrates: An Evolutionary Perspective (2001) p.620]; [about heart development] In the various tetrapod classes ontogenetic events essentially recapitulate the phylogenetic stages.[well established][VHOG] ostium secundum Wikipedia:Foramen_secundum foramen secundum VHOG:0001471 EMAPA:17863