Pancreatic Juice and Secretion

Pancreatic juice is a colorless liquid composed of water, salts, sodium bicarbonate, and enzymes secreted by the exocrine cells.

During digestion, chyme reaching the duodenum triggers secretin release, which stimulates the secretion and delivery of pancreatic juice into the small intestine.

Another duodenal hormone, cholecystokinin, released after a fatty meal also stimulates the release of pancreatic juice. 

The epithelial lining of the ducts secretes the non-enzymatic components of pancreatic juice that make it alkaline.

This alkalinity buffers the acidity of chyme, providing an ideal pH for the action of digestive enzymes in the small intestine.

The acinar cells secrete the enzymes present in pancreatic juice, including amylases to digest starch, lipases to digest lipids, and nucleases that digest nucleic acids.

However, the majority of enzymes in pancreatic juice are protein-digesting proteases, produced in an inactive form.

Trypsin, secreted as trypsinogen, is activated in the duodenum by enterokinase.

Trypsin then activates other protease precursors, such as chymotrypsinogen, procarboxypeptidase, and proelastase.