HISTOLOGICAL EXAMINATION OF THE A-V NODE AND A-V BUNDLE IN HUMAN HEARTS / 解剖学报

ABSTRACT

The morphology and position of the AV node and AV bundle were observed in 13 human hearts with serial sections. 1.the AV node is a long sagittal flatt ened structure, its transverse section is triangular in shape with a right convex surface, sometimes the cross section is fusiform or half oval in shape. Its size is 3.5x3.3x1.1 mm in adult. In 5 cases the endocardium lying on the right surface of the AV node is elevated.2.The AV node is situated in the upper border of the atrioventricular septum (between the levels of the attachment lines of the mitral and tricuspid valves). The adult AV node is 1.8-5.8 mm anterior to the coronary sinus orifice, 0.3-0.7 mm from the endocardium of the right atrium, 3.3-7.5 mm above the upper border of the septal leaflet of the tricuspid valve. The left surface of the AV node contacts with the central fibrous body.3.The AV node can be divided in 2 parts superficial and deep, the fibers of the super ficial part are longitudinal in sections and end in the lower border of the AV node. In one case, the deep part is subdivided in an upper part and a lower part. In the specimens in which the right atrial endocardium lying on the right surface of the AV node is elevated, the overlaying fibers end in the endocardium. At the upper border, right surface, and posterior margin of the AV node, there are atrial fibers ending to the AV node. 4. The adult AV bundle is 5.7-7.9 mm long, 1.1-1.5 mm in diameter. Its anterior part is on top of the muscular interventricular septum in 7 specimens, on its left surface in 3 specimens, and in the substance of the muscular interventricular septum in 2 specimens. In one case its course is very special, at first on the top of muscular interventricular septum, then at its left surface, finally in the substance of the right part of the muscular interventricular septum.