[Embryologic and anatomic considerations on the normal and pathologic formation of the cardiac septum. I....

A brief presentation of the normal embryological development of the human interatrial septum is made. The anatomical expression of each of its embryological components is described. Our classification of interatrial septal defect is enriched by their more precise anatomical description and by making a more correct morphogenetic interpretation, based on new information obtained by means of experimental embryology. Emphasis is made that absence of the interatrial septum does not preclude the diagnosis of viscero-atrial situs.