MVSc.

The structure and postnatal development of the oviduct in the Kuttanad duck was studied using 78 ducklings from day-old to 24 weeks of age. The material was collected from six birds in each group at fortnightly intervals. In the day-old duckling, the left oviduct could be seen as a thin, thread-like, translucent, straight tube towards the left side of the coelomic cavity supported by the dorsal and ventral ligaments. Uterus and vagina were recognizable even at this age. Among the 78 birds, persistent right oviduct could be detected in 20 birds. Signs of coiling of the oviduct were evident from 10th week onwards. All the five segments of the oviduct namely, infundibulum, magnum, isthmus, uterus and vagina could be clearly distinguished from 12th week onwards. Rapid development of the organ occurred between 16 and 18 weeks at which stage a few birds started laying. A spurt in growth of the oviduct was noticed between 18 and 20 weeks when all the birds started laying. The contribution of oviduct to the body weight was 3.47% at 24th week of age. During postnatal period, correlation between age and the length of the oviduct was more significant than with the oviduct weight. Magnum was the longest and most coiled component. Isthmus, uterus and vagina were relatively longer.
In the day-old duckling, the oviduct wall was not differentiated into different tunics and showed innermost simple columnar epithelium and subepithelial tissue. The lumen was flanked by characteristic low mucosal folds. At two weeks of age, the secondary mucosal folds started appearing. By 6th week, a very thin single layer of tunica muscularis appeared. The most dramatic growth and differentiation began at the age of 12 weeks when all the segments of the oviduct were differentiated morphologically and histologically. The tubular glands appeared as invaginations of surface epithelium and the mucosal folds became comparatively higher and broader at this age. Glands were absent in the funnel portion of infundibulum, magnum isthmus junction and vagina. The core of the mucosal fold showed numerous blood vessels. The lamina propria blended with the submucosa and muscularis mucosa was absent. Tunica muscularis was made up of inner circular and outer longitudinal smooth muscle layers and the thickness gradually increased from the cranial to the caudal direction. Distinct serosal tunic was visible in adult birds.
The funnel region of the infundibulum showed mainly low primary mucosal folds with a few secondary folds whereas in the neck region, numerous tertiary folds were also present. In the adult birds, there were four types of epithelial cells in the mucosa of neck namely non-secretory ciliated cells; non-ciliated mucous-secreting goblet cells; secretory cells other than goblet cells and lining cells of the tubular glands. Goblet cells increased in number caudally. At the infundibulum-magnum junction, groups of infundibular glands intermingled with tubular glands of the magnum.
In the magnum, mucosal folds were wider and higher and were lined by monolayered simple columnar ciliated epithelium with a few goblet cells. The glands of lamina propria were arranged in a radiating manner from the core to the periphery. Magnum-isthmus junction was characterized by complete absence of tubular glands. In the isthmus, by four weeks, the primary folds attained characteristic angular shape. In the adult birds, compared to all other segments of the oviduct, the glands in the isthmus were more loosely arranged. Regular alteration of both ciliated and secretory non-ciliated columnar cells was noticed in the lining epithelium. Isthmus - uterine junction showed an intermingling of glands within the lamina propria.
The mucosal folds of uterus were higher, leaf-shaped and were separated by deep furrows. Light cells and dark cells were visible in the lamina epithelialis. At 16th week, glandular development continued and the closely packed tubular glands in the mucosal folds were empty during non laying phase. But, prior to and during secretory phase, cells contained pale staining granules and after the shell formation, the cytoplasm was markedly vacuolated, with relatively large basal nucleus. Tunica muscularis was very thick with an inner circular and thicker outer longitudinal layers separated by loose connective tissue showing numerous vessels and nerves. At this age, smooth muscle fibres were observed to be extending to the core of the mucosal fold along with numerous collagen fibres.
At utero-vaginal junction the sperm storage tubules appeared at 12 weeks of age and were located in a thick ring of pushed-in mucosal folds found in the lumen with the vaginal folds on one side and uterine folds on the other. Mucosal folds towards the uterine side of the cranial utero-vaginal ridge contained transitional glands, which intermediate in appearance between sperm storage tubules and uterine glands. The sperm storage tubules were more sparsely distributed but had larger diameter than the transitional and uterine glands.
At two weeks of age, the vagina showed roughly triangular seven to eight primary folds lined by tall columnar cells interspersed with numerous goblet cells. Even at this age, tunica muscularis was well developed and differentiated into inner circular and outer longitudinal layers. By 12 weeks, the folds were characteristically filiform in appearance with secondary folds. The lamina propria was devoid of glands. Vagina showed the thickest tunica muscularis among different segments of the oviduct. Lamina propria of mucosal folds of the vagina showed large number of lymphocytes along with diffused blood cells from four weeks-old birds. As age advanced, all regions of the oviduct showed lymphocytes in diffuse as well as aggregated form which was maximum in the vaginal region.
The goblet cells found throughout the oviduct showed intense P.A.S. positive reaction. The presence of neutral and acid mucopolysaccharides was identified using P.A.S. and Alcian blue (pH 2.5) method in the epithelium of isthmus region; while in magnum, only the acid mucopolysaccharides were seen. The sperm storage tubules and transitional glands showed presence of lipid.
The presence of glycogen was observed only in the epithelial lining and tubular glands of isthmus region and was more pronounced in adult egg laying ducks with actively secreting glands. Marked alkaline phosphatase activity was seen in the uterus, isthmus and magnum. The activity of Acid phosphatase was observed in the epithelium and tubular glands of isthmus, shell gland and vagina.