Abstract

Normal embryonic development of human heart is studied with special emphasis to the formation of atrioventricular and ventriculoarterial connections and their significance in congenital heart disease. Twenty nine human embryos and 8 chick embryos are used in this study. Human embryos are analyzed by reconstruction of serial section slides and chick embryos are microdissected and examined by scanning electron microscopy. In the early cardiac development (Streeter horizon 12), bulbo-ventricular fold divided two ventricles first. The atrioventricular canal is incompletely divided and the canal was in contact neither with septum primum nor with ventricular septal crest. Infundibular and truncal septa were not seen. The division of A-V canal was observed during the stages 14-15. Septation of truncus arteriosus (Streeter horizon 15-17) was followed by septation of bulbus cordis (Streeter horizon 16-17). The shortening of mitral-aortic distance and downward left shift of aortic valve occured after the trunco-infundibular septation and finally the secondary interventricular formen closed at the end of seventh week (Streeter horizon 20-21).

• Keywords: Cardiac development;Morphological study;Embryo;Bulboventricular malformation;