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zymogen granules intralobular collecting duct intercalated duct zymogen granules centroacinar cell FIGURE 17.20

Pancreatic acinus and its duct system, a. In this photomicrograph of a thin, H&E-stained plastic section, an intercalated duct can be seen beginning within a pancreatic acinus. The cells forming the duct within the acinus are the centroacinar cells. The eosinophilic zymogen granules are clearly seen in the apical cytoplasm of the parenchy mal cells. x860. b. In this schematic diagram, observe the beginning of the intercalated duct. Note the location and shapes of the centroacinar cells within the acinus. They represent the initial lining of the intercalated duct, which drains into an intralobular collecting duct.

acinar cells intralobular collecting duct intercalated duct centrally placed, flattened nucleus and attenuated cytoplasm, which is typical of a squamous cell.

Centroacinar cells are intercalated duct cells located in the acinus

Centroacinar cells are continuous with the cells of the short intercalated duct that lies outside the acinus. The structural unit of the acinus and centroacinar cells resembles a small balloon (the acinus) into which a drinking straw (the intercalated duct) has been pushed. The intercalated ducts are short and drain into intralobular collect ing ducts. There are no striated (secretory) ducts in the pancreas.

The complex, branching network of intralobular ducts drains into the larger interlobular ducts, which are lined with a low columnar epithelium in which enteroendocrine cells and occasional goblet cells may be found. The interlobular ducts, in turn, drain directly into the main pancreatic duct, which runs the length of the gland parallel to its long axis, giving this portion of the duct system a herring-bone-like appearance (see Fig. 17.19). A second large duct, the accessory pancreatic duct, arises in the head of the pancreas.

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