Conclusion
We conclude that the RN connects with the AVN, which suggests direct electrical conduction between them. The entrance of the atria into the AVN is the distal part of the RN. The fast pathway of the AVN is strongly suggested by the structure of the RN and its extension. The level of the start of the CN is a more complex region than previously described. First, it stretches downward, forming the transitional area between the His bundle and AVN; second, it extends backward, forming the main body of the CN; and third, it accepts the insertion of the end of the RN.