Histology of the small intestine in the common pheasant (Phasianus colchicus): A scanning electron microscopy, histochemical, immunohistochemical, and stereological study

The present investigation was conducted to investigate the histology, immunohistochemistry, stereology, and ultrastructure of the small intestine in the common pheasant (Phasianus colchicus) using light and scanning electron microscopy (SEM). Ten birds were included in the study. The obtained findings revealed that three parts in the small intestine namely duodenum, jejunum, and ilium constituted of four layers from innermost to outermost including tunica mucosa, tunica submucosa, tunica muscularis, and tunica serosa. All parts of the small intestine had simple columnar epithelium with goblet cells reacted with Periodic Acid-Schiff and Alcian Blue stains especially in the jejunum and ileum. The cells on the tip of the duodenal villi showed immuno-positive staining for Sox9 protein, while the jejunum and ileum were negative. The jejunum had longest villi; however the duodenum had deepest crypt (p < .05). The villus surface of jejunum was significantly higher than duodenum and ileum (p < .05). SEM images revealed that the duodenum had cauliflower and leaf-like villi with plicas and recess between them. Jejunum had finger-like villi with a velvety view. The shape of the ileal villi was like that observed in the jejunum with slight differences. In conclusion, the jejunum was the most prominent region in the small intestine in terms of morphologic and morphometric features, which could be attributed to the absorption of more nutrients in this area. These obtained findings would be useful to improve the knowledge in the field of histophysiology properties of the bird's digestive system.