Gall bladder is a small pouch found attached to the liver and stores bile. A total of 24 guinea pigs of four different postnatal ages with six animals each were collected from the Department of Laboratory Animal Medicine as per the Ethical committee approval. Gall bladder were dissected, fixed and processed for paraffin embedding. Sections of 4-5 μm thickness were cut and used for the routine and special histological staining techniques. The wall of the gall bladder consisted of tunica mucosa, submucosa, muscularis and serosa in all the postnatal ages. The tunica mucosa of gall bladder consisted of irregular folds with primary, secondary and tertiary folds. All the folds were visible in the gall bladder of postnatal ages with the folding increased as age increased. Guinea pigs of 0-2 weeks of age showed only primary folds of less height. The tunica mucosa consisted of lining epithelium and lamina propria. Mucularis mucosa was not observed in all ages. Lamina propria and submucosa formed a continuous layer. The lining epithelium was simple tall columnar epithelium with irregular microvilli at the luminal border. Lamina propria – submucosa consisted of loose of connective tissue with collagen, reticular fibres, fibroblasts, lymphocytes and blood vessels. Tunica muscularis was a fibromuscular coat, consisted of loose arrangement of smooth muscular layers in longitudinal and circular fashion. Tunica serosa covered the external surface of the gall bladder in all ages and consisted of loose connective layer which was upcovered by a single layer of mesothelium.

Highlights

• Guinea pigs of group I showed only primary folds.
• Goblets cells were not observed in epithelium.
• Muscularis mucosa and glands were not observed.