A comparative LM and SEM study of the structure of the mucosal glands of the gallbladder in two species of canids: the dog and the Chinese raccoon dog.

The studies were performed on the mucosa of the body of the gallbladder in the dog and Chinese raccoon dog, species belonging to the Canidae family. The mucosal glands in both species mostly have the form of alveolar or short tubular secretory units without excretory ducts and are situated in the middle part at the bottom of the crypts surrounded by folds of the mucosa. Sporadically we observed the mucous intraepithelial glands. The results of the light and scanning electron microscopic observations indicate interspecies differences in the density, type and size of secretory units and also their openings. In the raccoon dog the number of secretory units is 30 times greater than in the dog and the units are predominantly simple glands with small openings. In the dog mostly 2 or 3 secretory units with common wide openings were observed. The SEM images of the NaOH macerated mucosa of the gallbladders showed a connective tissue framework around the glands composed of flat lamina with an irregular pattern of fine collagen fibres and numerous fenestrations. The collagen network around the openings of the glands is more compact and provides mechanical support for the glands of the gallbladder.