الفهرس 
EMBRYOLOGY AND DEVELOPMENTOnly 14 pages are availabe for public view
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Abstract
Introduction & Aim of the work: Owing to its specified absorptive and immunological significance, the present research was designed to study the wall of ileum at the region of Peyer’s patches in rabbit both by light and transmission electron microscopes in a view to identify its structural features. Materials & Methods: Forty adult male rabbits were used in this study, and specimens of ileum at the region of Peyer’s patches were taken and divided into two groups: some specimens of the first group were fixed in 10% foramalin saline while others are fixed in Bouin’s solution . After impregnation in paraffin, 5m thick sections were cut and stained with hematoxylin and eosin, PAS, Mallory trichrome and Gordon and Sweet’s method for reticular fibers. Specimens of the second group were trimmed into finer fragments which were processed for epon plastic embedding, semi thin sections were stained with toluidine blue and examined by light microscope while ultrathin sections were subjected to an electron microscopic study. Results: The results of this study revealed that the microscopic composition of the wall of the ileum was similar to the general structure of intestinal wall, being formed of the mucosa, submucosa, musculosa and serosa despite it had an extra-unique immunological structure known as Peyer’s patches. The most popular cell type was the columnar absorptive cells which covered the villi and lined the intestinal crypts. Despite they were significantly fewer over Peyer’s patches, goblet cells were the second mostly commonly encountered cells in mucosal epithelium of the ileum . Downside the intestinal crypts, the epithelial lining contained many Paneth cells that were characterized by their apical granules, these granules were previously explained as having lysosomal and enzymatic activities. A unique structure characterizing the lower part of the ileum was the immune system that forms basically of aggregated lymphoid follicles to compose what is known as Peyer’s patches, each of these follicles was found to be composed of dome, corona, germinal center and interfollicular area. The mucosal epithelial covering the corona had a prevalence of M - cells that had irregular outline and short apical microvilli. Post capillary venules were commonly seen in the wall of the ileum. They were similar to most venules in composition despite they contained a large number of migrating lymphocytes across their walls . A factor that merits further study is their high cuboidal endothelial lining. Conclusions: The results of this study were discussed on the light of some of the historical and current literatures dealing with the developmental, structural and functional aspects of the different tissues composing the ileum in general and at the region of Peyer’s patches in particular.