Summary

Schematic representation of the atrioventricular bundle of His. The bundle, represented in red, originates near the orifice of the coronary sinus, undergoes slight enlargement to form the AV node. The AV node tapers down into the bundle of HIS, which passes into the ventricular septum and divides into two bundle branches, the left and right bundles. Sometimes the 'left and right bundles of His' are called Purkyne or Purkinge fibres. The ultimate distribution cannot be completely shown in this diagram.

This image is misleading. Although it correctly places the SA and AV nodes in the right atrium, it appears as though there are only two papillary muscles in the right ventricle and three in the left ventricle. The opposite is actually true. The papillary muscles attach to chordae tendinae which then attach to the leaflets of the AV valves, preventing prolapse. The left AV valve is the mitral or bicuspid and only has two leaflets and therefore two papillary muscles. The right AV valve is the tricuspid and should have three papillary muscles corresponding to the three leaflets of the valve.

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