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Abstract The present work was carried out on eighty five female geese at three different stages of development: immature, sexually mature, and egg laying period. Immediately after the geese were humanly scarified and eviscerated, pieces of the left oviduct were taken, fixed in 10% buffered neutral formalin and processed until paraffin sections were prepared for the light microscopic study. In addition, pieces of the left oviduct were fixed, in 2.5 % glutaraldehyde and processed until ultra-thin sections were prepared for transmission E/M examination. The term oviduct in the geese is used to describe the entire reproductive duct. Only the left oviduct is present in the adult bird. The development of the right oviduct of female geese is totally arrested very early in embryonic life. The left oviduct, anatomically speaking, is divided into infundibulum, magnum, isthmus, uterus and vagina, each of these anatomical divisions has special structural and functional features. Microscopically, the oviduct has the characteristics of a tubular organ, whose wall is formed of tunica mucosa, submucosa, muscularis and serosa or adventitia in the most caudal part of the oviduct. The oviduct of immature birds is simple in structure, and its wall is formed of tunica mucosa, submucosa, muscularis and serosa. The tunica mucosa shows longitudinal folds which, appears in cross section as short primary folds. In immature geese, the covering epithelium of the mucosal folds is a simple epithelium, and is formed of light and dark cells, which are columnar in shape. However, the dark cells are the predominant types and exhibit rod-shaped darkly stained nucleus, and acidophilic cytoplasm. On the other hand, the light cells are fewer in number and exhibit oval vesicular nucleus near their base. The propria-submucosa is highly cellular; its vascular connective tissue contains lymphocytes and fibroblasts. The lamina propria exhibits a collection of small lymphocytes (lymphoid follicles), -and blood vessels. The tunica muscularis does not appear as a definite layer or bundles of fibers, but appears as isolated smooth muscle fibers which run within the vascular connective tissue. In addition, the oviduct is surrounded with ill-defined serosa in most parts, and adventitia in the most caudal part of the vagina. When the geese reaches the age of sexual maturity and the egg laying period, the wall of the oviduct appears to be formed of well-developed four layers: tunica mucosa, submucosa, muscularis, and serosa. The tunica mucosa shows a well developed longitudinal folds which appear in cross section as long primary folds that may be divided to show secondary folds, and may have tertiary folds, especially in the infundibulum and vagina. The lining epithelium of the fold is ciliated pseudostratified columnar epithelium, formed of ciliated columnar-shaped cells, secretory non-ciliated columnar cells, and basal cells. The ciliated cells are more predominant in infundibulum and vagina. The lamina propria is fibrous connective tissue containing fibroblasts, lymphocytes, blood vessels, collagen fibers and tubular glands which deeply project from the epithelium into the lamina propria. This is especially true in the glandular parts of the oviduct, which are the neck part of the infundibulum, magnum, isthmus, and uterus. The glandular parts are also found in vagina, not as secretory glands but rather as a store house for spermatozoa. The tunica submucosa is made of fibrous connective tissue, while the tunica musculosa is a well-developed layer of smooth muscle fibers, which may be circular or longitudinal according to the place where is the fibers are found. The smooth muscle, layer is the thickest in the region of vagina, and the serosa, forms the external sheath of the oviduct. The present study reveals that the neutral and acidic mucopolysaccharides do not exist in the lining epithelium of any part of the geese oviduct of immature birds. This could be explained by the fact that the primitive epithelial cells are still did not differentiate into ciliated and secretory cells, and there were no secretions produced. However, once the geese reaches its age of sexual maturity, cell differentiation occurs, and the secretory cells gain their secretory activity. Expectedly, both the neutral and acidic mucopolysaccharides are present in the lining epithelium of the oviduct of sexually mature birds. The neutral mucopolysaccharides are also present in the glandular cells of infundibulum neck, magnum, isthmus, uterus and the sperm storage glands in the vagina. In contrast to that, the acidic mucopolysaccharides do not exist in the glandular cells of infundibulum neck, magnum, isthmus, and uterus but exist in the sperm storage glands in the vagina. TEM study reveals that the ultrasructures of the surface epithelium of the geese oviduct showed two types of cells, namely, ciliated and non-ciliated granular or secretory cells. The secretory cells possese,s high content of mitochondria, free ribosomes, RER profiles, and lysosomes. The ciliated cells are narrow with an expanded apex carrying the cilia and exhibit elongated or irregularly- shaped, euchromatic nuclei, which were located in the wide luminal regions of the cells. Cilia are cylindrical in shape and are identical in length. The present study documented that the secretory granules are present either in the secretory cells of the lining epithelium, or in the cells lining the proprial glands. The secretory granules are electron- lucent, of medium to large size, and are present either above the level of the nucleus (supra-nuclear) or under the level of the nucleus (infra-nuclear. |