Meckel's Diverticulum in Adult Geese (Alopochen egyptiacus): A Comprehensive Study of Structure Using Histological, Electron Microscopy, and Immunohistochemical Methods.

The intestine plays an important role in mediating between the bird and its nutritional environment. The yolk stalk, also known as Meckel's diverticulum, is a landmark between the jejunum and ileum. This work aimed to investigate the anatomical, histological, and electron microscopical features of cellular components of the Meckel's diverticulum (MD) in adult geese. The intestine was dissected from the bird's body cavity, and Meckel's diverticulum was exposed and prepared for light and electron microscopical examinations. Our results revealed that the MD mucosa is thrown up into villi and crypts, and the mucosal epithelium is a columnar epithelium with goblet cells as well as intraepithelial lymphocytes. Lymphoid follicles and numerous immune cells were demonstrated within the lamina propria. The mucous glands were also observed within the lamina propria and amongst the lymphoid follicles. The lining epithelium of MD appeared with different staining affinities: dark cells (electron-dense) and light cells (electron-lucent) contained few mitochondria and more secretory vesicles, while dark cells contained more mitochondria and fewer secretory vesicles. Immunohistochemical analysis of MD revealed positive immunoreactivity for several markers, such as CD 117, chromogranin, PLCβ, cytokeratin, MHC II, and S 100. Taken together, our findings suggest that MD is considered an immune organ in adult geese.