Multiple myenteric networks in the human appendix

The general histological organization of the appendix, including its innervation, is believed to be generally similar to that of the large intestine. However, several authors described an unusual arrangement of the myenteric ganglia within the appendiceal muscle, but conflicting reports do not allow clear conclusions on this matter. The aim of this work was to examine the appendiceal innervation in detail. The myenteric plexus of the human appendix was examined using sections and whole mount preparations. Human small and large intestines were used for comparison. The nerves were stained using immunohistochemistry, enzyme histochemistry for NADPH-diaphorase, and vital staining with 4-(4-diethylaminostyryl)-methylpyridinium iodide. Appendices from rabbits were also studied. In most cases, the innervation of the external muscle of the appendix consisted of three concentric networks of ganglia. These networks were located both between the circular and longitudinal muscle layers and within them. The middle network made connections with the other two. Such arrangement was not observed in the human small and large intestines. The myenteric plexus in the rabbit appendix displayed a much smaller degree of three-dimensional distribution compared with that of the human appendix. It is concluded that the myenteric plexus in the human appendix consists of several distinct networks, and appears to be unique in comparison with the other parts of the intestine.