Histological and Histochemical Studies on the Esophagus, Stomach and   Small Intestines of Vara-nus niloticus
  The aim of the current study was to investigate the morphological structure of one of the most common reptilian species in Egypt, Varanus niloticus or Nile monitor. Specimens for histological examination were collected from the esophageus, stomach and small intestine of the Nile monitor and processed for paraffin embedding. Sections were stained with haematoxylin and eosin for general morphology. Periodic Acid Schiff's (PAS) and Alcian Blue (AB) staining methods were applied to detect the different types of the mucous con-tents of the gastro-intestinal tract. Some paraffin sections were stained with Grimelius silver impregnation technique for localization of the enteroendocrine cells. The folded esophageal mucosa had ciliated columnar epithelium with mucous secreting goblet cells, which stained positive with PAS and AB. The esophageal mucosa was folded and the lining epithelium was ciliated columnar epithelium with mucous secreting goblet cells, which stained positive with PAS and AB. The stomach was divided into fundic and pyloric regions. The mucosa was thrown into gastric pits, into which the gastric glands opened. The surface epithelium was mucous secreting columnar cells and stained positive with PAS but negative with AB. The fundic gland was made by oxynticopeptic cells and few mucous cells, while the entire pyloric gland was made by mucous cells stained positive for both PAS and AB. The small intestine showed many villi but occasional poorly developed intestinal crypts were. The intestinal mucosa was lined with absorptive columnar epithelium with goblet cells, which stained positive with PAS and AB. Enteroendocrine cells were of different shapes; rounded, spindle, oval or pyramidal and were localized in the surface epithelium of the esophagus and small intestine, and among the cells of the gastric glands. 
Ahmed YA, El-Hafez AAE, Zayed AE
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