RESUMEN
OBJECTIVE: To investigate the development of the enteric nervous system(ENS) in the middle stage(the 4th approximate, equals 6th months) of human embryogenesis. METHODS: A histologic evaluation of the clonic enteric nervous system was done using NADPHd histochemistry, PAP immunohistochemistry, with anti-PGP 9.5 and anti-S-100 protein. RESULTS: During this stage of embryology three things were noted. (1)The nerves in the myenteric layer increased markedly. This was shown by the PGP 9.5 immunoreactive nerves spreading out and the S-100 protein immunoreactive nerves forming a "bamboo basket"pattern. (2)The whole myenteric colon showed nitrigeric nerves paralleling the growth of the myofibers in the circular muscle layer. Nitrigeric perikara were rarely found in the extrinsic submucosal layer.(3) In the whole-mounted preparations reactive nerves formed the complex nerve net in the myenteric layer. CONCLUSION: The middle stage of embryogensis is very important to the development of the colon ENS.