Ontogenesis of the structural elements of the heart.

A review of the birth locus and the first developmental stages of cardiomyocytes and Purkinje cells in the chick embryo is presented in the light of recent experimental results. Experiments done in vitro have shown that the stage of 2 somites is an important morphogenetic phase, characterized by mutual identification, selective adhesion and spatial organization of the putative cardiac cells of the splanchnopleural sheet in the cardiogenic area. Many experimental data suggest that the neural crest cells moving through the corridor of the dorsal mesocardium, as well as the cholinergic system related to them, may play a role of myogenic inductors on the mesothelial putative cardiac cells. In addition, other experimental findings suggest that the Purkinje cells of the conduction system may have a crestal origin. This hypothesis is well grounded, although the origin of Purkinje cells remains to be clarified.