الملخص

The purpose of this study was to describe, comparison the histological structures and histochemical of the histological layers in the different parts of the duodenum, with observation of the reactions of cells and tissues using histochemical stains (PAS, AB-PAS and toluidine blue). The study was carried out on twelve samples of duodenum of each of squirrel and hamster. The duodenum divided into proximal part, middle part and distal parts. six specimens were taking from squirrel and six specimens from hamster. The duodenum is squirrel and hamster fixed in 10% formalin for 24 hours and treating by routine histological technique. The duodenum consists of four main tunicae that is mucosa, submucosa, muscularis, and serosa. The mucosa layer is consists of three secondary layers the first layer is epithelial lining layer, lamina propria, and end layer is muscularis mucosa. The epithelial covering comprises simple columnar epithelial tissue composed of the columnar cells and goblet cells. The lamina propria under epithelial layer that contains simple straight tubular glands called the intestinal glands or the crypt of Lieberkühn. The muscularis mucosa that end layer is composed of the a very thin, single layer of the smooth muscle fibers arranged circularly. The submucosa layer consists of the dense connective tissue, while the tunica muscularis appears composed from two layers of smooth muscle fibers. The tunica serosa consists from a loose connective tissue that is covered by a mesothelium.