Morphology of the pancreatic duct system in mammals.

The morphology of pancreatic excretory duct segments was reviewed in mammals. The fine structure of the epithelial lining was described in intercalated ducts, intra- and extralobular ducts, and in major pancreatic ducts. Morphological characteristics of the various cell types comprising to the duct epithelium were detailed. Principal cells in the epithelial linings of interlobular and major pancreatic ducts ("Wirsungiocytes") were discussed with respect to their appearance as either clear or dark variety. In addition, the capacity of both these cell types in elaborating mucoid glycoprotein, secretions was considered and intra- and extraepithelial mucoid glands of major pancreatic ducts (ductular glands, accessory glands) was described. Finally, the wall composition of the various excretory duct segments was described. The presence of smooth muscle cells, myofibroblasts, and a peculiar periductal vascular plexus in major interlobular ducts and in main pancreatic ducts was emphasized.