Abstract
The present study elucidated the histoarchitecture of the upper digestive tract (UDT) of six Spur-winged geese (SWG), a wildfowl species of the Sudano-Sahelian wetlands of northern Nigeria. Tissue samples collected from different parts of the UDT were processed by the routine paraffin technique of light microscopy. The beak was lined by stratified squamous keratinized epithelium. The underlying dermis consisted of dense areolar tissue, blood vessels, and encapsulated nerve endings of Herbst corpus-cles. The apical part of the tongue was lined by stratified squamous epithelium, which was heavily cornified on the ventral surface. The lingual submucosa comprised a mass of compound tubular mucous glands that exhibited moderate reactivity to Alcian blue. The esophagus was lined by stratified squamous non-keratinized epithelium, while the subepithelial area showed a few lymphatic nodules and polymorphic alveolar mucous glands. The mucosal glands were modified at the esophageal-proven-tricular junction into crypt-like folds. The proventricular wall comprised mainly proventricular glands, consisting of straight alveolar tubules lined by oxyntico-peptic cells, especially towards the basal portion. The proven-tricular plicae at the isthmus were modified into organized gizzard glands. The gizzard mucosa was lined by a hard cuticle layer. The gizzard-duodenal junction presented mucosal folds of variable heights, lymphatic nodules, and duodenal villi.