The duct cell is a minor cell type of the pancreas, which comprises 10% of the cells and 4% of the volume of the pancreas (39). The predominant acinar cells are much denser than the other cell types because of their large content of zymogen granules (145), thus the duct cells contain less than 4% of the pancreatic protein. The duct cells comprise a tubular epithelium through which the secretions of the acinar cells (digestive enzymes in a small volume of chloride-rich fluid) reach the duodenum. The duct system adds a large volume of a bicarbonate-rich fluid that aids the movement of the digestive enzymes through the duct system and neutralizes stomach acid in the duodenum, although there is considerable species variation in the details of duct cell function (21, 22) . The smallest of the pancreatic ducts, the intralobular ducts (ductules), are in direct epithelial continuity with the acinar cells and tend to project into the acinus as centroacinar cells. Ductular cells comprise about 80% of the cells of the duct system (75). Ductules drain into interlobular ducts and these drain into one or more main ducts. As duct size (luminal diameter and number of cells in circumference) increases, the height of the epithelium and the thickness of surrounding connective tissue increases (39). Duct cells generally exhibit an unspecialized cytoplasm containing a few mucin secre­ tory granules in interlobular and main ducts, apical microvilli, a single apical cilium, and extensive interdigitations of lateral plasma membrane. Small numbers of goblet, brush, and endocrine cells are scattered among the principal cells of interlobular and main ducts (39, 96, 119).