Acute pancreatitis is the sudden inflammation and hemorrhaging of the pancreas due to destruction by its own digestive enzymes—a process fittingly called autodigestion.
Most of the time the disease is actually relatively mild, but it can easily become severe, so it's critical to diagnose and treat it quickly.
The pancreas is a long, skinny gland the length of a dollar bill and is located in the upper abdomen, or the epigastric region, behind the stomach.
It plays endocrine roles—for example, alpha and beta cells make hormones like insulin and glucagon that are secreted into the bloodstream, but it also plays exocrine roles— for example, acinar cells make digestive enzymes that are secreted into the duodenum to help digest food.
These pancreatic digestive enzymes break down macromolecules like carbohydrates, lipids and proteins found in food, but these macromolecules are also found in the cells of the pancreas.
To protect the pancreas, the acinar cells manufacture inactive forms of the enzymes called proenzymes, or zymogens.
These zymogens are normally activated by proteases which cleave off a polypeptide chain, which is kind of like pulling the pin on a grenade.
For additional security, the zymogens are kept away from sensitive tissues in storage vesicles called zymogen granules, and are packaged with protease inhibitors that prevent enzymes from doing damage if they become prematurely active.
To digest a meal, these zymogens are released into the pancreatic duct, and delivered to the small intestine where they are activated by the protease trypsin.
Trypsin is a pancreatic digestive enzyme that is produced as the zymogen trypsinogen.
Normally, trypsinogen isn’t activated until it is cleaved by protease enteropeptidase which is found in the duodenum. But if trypsinogen and these zymogens become activated too early, then it can cause acute pancreatitis, and this might happen as a result of any injury to the acinar cells, or anything that prevents the normal secretion of the proenzymes into the duodenum.