Development of atrioventricular specialized tissue in human heart.

Abstract

The ontogenetic development of the atrioventricular specialized tissue has been studied in 9 hearts processed by paraffin-embedding techniques, and in 8,fresh hearts prepared by cryostat sectioning and processed using histological and neurohistochemical techniques. The results indicate that the atrioventricular node has a dual origin, derived in part from left sinus horn musculature and in part from atrioventricular canal musculature. This mode of development gives the node a tri- laminar appearance. Other remnants of the atrioventricular canal musculature persist as ring bundles in the atrial margins of the atrioventricular orifices. The results also show that the specialized tissue is formed from a separate cellular population to the myocardium. This population differentiates in situ in the ventricular cavities to form the definitive A V specialized tissue. The results are compared and contrasted with previous investigations of the A V specialized tissue.