Topographical and morphometrical study of the atrioventricular junctional area of the cardiac conduction system in the Macaca fascicularis Raffles, 1821.

The morphology of the atrioventricular (AV) junctional area is a subject for great controversies. The present work studies this region in 2 hearts of M. fascicularis adult female perfused with Bouin fluid, serial sectioned in frontal plane and stained by van Gieson trichromic method. A three-dimensional wax reconstruction of the AV specialized tissue was performed. The areas of the AV bundle and left bundle branch (LBB) cross-section were calculated by point-counting. The results showed that the junctional AV region in M. fascicularis is approximately similr to the same region in the human heart. The AV node presents compact and transitional portions. The cardiac central fibrous body is well developed and gives off an incomplete septum of connective tissue interposed between the terminal portion of the AV node and the beginning of the AV bundle. The reconstruction showed that the right bundle branch (RBB) is the direct continuation of the AV bundle while the LBB is a broad left side detachment. The average diameters of the AV bundle, LBB and RBB proved to be respectively 867.08 micron and 126.65 micron. The length and the volume of the AV bundle were respectively 406.86 micron and 0.223 mm3.