Expression of Neuron-Specific Enolase and S-100 in the Ileum and Ileocecal Junction in the Human Fetuses at Various Gestational Ages

Background and Objectives: The purpose of this study was to study the histogenesis and neuroanatomy of the human fetal ileum and ileocecal junction at various gestational ages (15, 18, 20, 28, and 32 weeks) using neuron-specific enolase (NSE) as a neuronal marker and S-100 as a glial marker for the enteric nervous system. Materials and Methods: For this study, five aborted normal fetuses were obtained from the fetal repository of Department of Anatomy. The ileocecal part of the small intestine of these fetuses was dissected, processed, and sectioned and stained with hematoxylin and eosin and cresyl violet. Immunohistochemistry was performed using antibodies to NSE and S-100 and observed under a BX61 Olympus microscope using a DP71 camera. Results: The myenteric and submucosal plexuses of terminal ileum and ileocecal junction show immunoreactivity for both NSE and S-100 by 20 weeks. The development of myenteric plexus is more advanced than submucosal plexus. The immature neurons at 15 weeks progressively mature with distinct cell processes at 32 weeks. The mature ileocecal junction is composed of two outer circular muscle layers and a single inner longitudinal muscle layer. At 32 weeks, ileocecal valve was visualized. Interpretation and Conclusions: Our study provides the morphological evidence of the immunoreactivity in the ganglion plexus and the development of ileum and ileocecal junction at different developmental stages. It also substantiates the concept of ileocecal junction being an intussusception of ileum into the cecum