The main pancreatic duct opens into the summit of the major duodenal papilla, usually in common with the bile duct. Proteolytic enzymes are secreted as zymo gen s - inactive precursors of the enzymes. They are activated in the lumen of the digestive canal. The enzyme enteropeptidase is associated with the brush border of enterocytes. It catalyses the conversion of trysino gen into trypsin.
Trypsin can activate a number of the other pancreatic zymogens.
While the enzymes are secreted by the secretory cells of the pancreatic acini, the bulk of fluid and bicarbonate ions of the pancreatic juice are secreted by the cells which form the intercalated ducts of the pancreas . Identify the connective tissue between the lobes and lobules and try to find interlobar or interlobular excretory ducts. Their outline is often irregular and their lumen is lined by a tall columnar epithelium. If you find a large duct you may see a number of smaller ducts streaming towards the larger duct and, occasionally, connecting with it. The overall appearance of the pancreas is that of a serous gland.