Histological and Histochemical Characterization of the Small Intestine of German Nun Pigeons

The present study aimed to describe the histological and histochemical characteristics of the small intestine in adult German Nun pigeons (Columba livia domestica). Samples from the duodenum, jejunum, and ileum were collected from six adult birds of both sexes and processed using routine hematoxylin and eosin (H&E) staining, as well as periodic acid–Schiff (PAS). The three distinct segments of the small intestine consist of the characteristic four tunics including mucosa, submucosa, muscularis externa, and serosa. The mucosa is lined by simple columnar epithelium with numerous goblet cells, which produce mucus to make easy food passageway and protect the intestinal lining. The villi well-developed, crypts of Lieberkühn are noticed, indicative of an increased absorptive capacity. The lamina propria composed of connective tissue with lymphoid cells. The muscularis mucosa and submucosa are thin or lack, while the muscularis externa contains inner circular and outer longitudinal smooth muscle layers that assist in peristalsis. Histochemical staining revealed a strong reaction for mucopolysaccharides in goblet cells, especially in the jejunum.