TY  - BOOK
AU  - Shyla Paulose 
AU  - Ommer P A (Guide)
TI  - Postnatal development of upper digestive tract in the Duck
U1  - 636.089 1 
PY  - 1990///
CY  - Mannuthy
PB  - Department of Anatomy, College of Veterinary and Animal Sciences
N2  - The structure and postnatal development  of the upper digestive tract of ducks at different stages of growth was studied using 72 white pekin ducklings aged from day-old to 180 days for the proper understanding of their functional peculiarities. The growth, morphology and histology of the tongue, pharynx, oesophagus and crop, proventriculus and gizzard were studied using  six birds at each  age group. The oesophagus and the gizzard attained the maximum growth by 75 days whereas the tongue, pharynx, and the proventriculus at 150 days of age.

	The tongue, pharynx and oesophagus were lined by stratified squamous epithelium. Herbst’s, Grandry’s and Meissaner’s corpuscles, ganglion cells and encapsulated spherical bodies were present in the tongue. Filiform, fungiform and conical papillae, many taste buds, anterior and posterior lingual holocrine mucous glands were  observed in the tongue. The tip of the entoglossal bone remained cartilaginous and showed signs of ossification from eighth day of age.

	Within the choanal slit, cavernous tissue covered by pseudostratified ciliated columnar epithelium was present. In pharynx, pharyngeal tonsils, palatine, sphenopterygoid and laryngeal salivary glands were noticed. At the inlet of the larynx, the epithelium changed to pseudostratified ciliated columnar. The laryngeal cartilages were cricoids, procricoid and paired arytenoids.

	The oesophagus consisted of longer cervical part, spindle shaped  crop and short thoracic part. The longitudinal mucosal folds were more at the crop and the microscopic papillae appeared on the crop and thoracic oesophagus from 15 days of age. The mucous glands were present throughout the esophagus and crop. The muscularis mucosa and submucosa were absent. Tunica muscularis consisted of inner longitudinal and outer circular layer of smooth muscles. The adventitial cost was replaced by a layer of serosa in the thoracic part. A well developed oesophageal tonsil was present at the oesophage –proventricular junction.

	The elongated proventriculus had narrow cranial and wider caudal ends with numerous small papillae containing the opening of the proventricular gland. The mucosal folds were lined by cuboidal to columnar cells. The superficial proprial glands showed zonation. The unilobular compound tubular glands were lined by oxyntico-peptic cells which had a dentate appearance. In the day –old ducklings, the lobules were elongated in the anterior and middle part and in the posterior portion they were small and polygonal in shape. From 15 days onwards, most of the gland lobules were round or polygonal in cross section. The central cavity of the gland and the duct were lined by tall columnar cells which were PAS positive. The muscularis mucosa as a 
distinct layer was not seen and the submucosa was absent, Tunica muscularis consisted of inner and outer longitudinal and middle circular layer of smooth muscles and invested by the serous layer. At the isthmus, the proventricular glands and the outer longitudinal muscle layer were absent and the lamina propria contained glands similar to gizzard glands.

	The gizzard had greater dorso-ventral diameter than cranic –caudal diameter except in day-old ducklings in which the reverse was true. The tendon layer was thickest at the tendinous aponeurosis and absent in the blind sacs. The lateral muscle consisted of single layer of circular smooth muscle whereas the blind sacs had inner longitudinal and outer circular layers of smooth muscle. Submucosa was dense and the muscularis mucosa was absent. The simple  tubular gizzard gland was lined mainly by chief cells. The chief cell granules and the luminal contents showed similar reactions in PTAH and trichrome staining. The surface epithelium showed papillary projections and were lined by tall columnar cells which showed supranuclear PAS positive reaction. The thickness of the glandular layer and the gizzard lining consisted of arrays of vertical columns secreted by the tubular glands and the matrix produced by the surface cells. The lining was strongly adherent to the musculature and could not be peeled off. The blood and nerve supplies to these organs were studied using embalmed carcasses and angiograms

UR  - http://krishikosh.egranth.ac.in/handle/1/5810094973
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