A deeper dive into the two functional components of the pancreas: exocrine and endocrine

One Organ, Two Different Functions

The pancreas is really two glands that are mixed together into one organ with two separate functions.

Digestion (Exocrine)   

Acinar cells

The bulk of the pancreas is composed of “exocrine” (exo=outward) cells that produce enzymes to help with the digestion of food.

These exocrine cells are called "acinar cells" and they produce and transport enzymes that are released into ducts and then passed into the duodenum (the first part of the small bowel), where they assist in the digestion of food.

Blood Sugar (Endocrine)   

Islets of Langerhans - illustration by Kyoungran Eun

The second functional component of the pancreas is the "endocrine" pancreas. The endocrine pancreas is composed of small islands of endocrine (endo=within) cells. The islands are called the islets of Langerhans.

These endocrine cells release hormones such as insulin and glucagon into the blood stream, which maintain the proper level of sugar (glucose) in the blood. Blood sugar is used by the body for energy.

Why is this Important?

Understanding the two functions of the pancreas is important because:

Large tumors of the pancreas will interfere with both of these important bodily functions.

  • Exocrine: when tumors block the exocrine system, patients can develop pancreatitis and pain from the abnormal release of digestive enzymes into the substance of the pancreas instead of into the bowel, and they can develop digestive problems, such as diarrhea, from the incomplete digestion of food.
  • Endocrine: when tumors destroy the endocrine function of the pancreas, patients can develop sugar diabetes (abnormally high blood sugar levels).

Tumors can arise in either component, exocrine or endocrine.

  • Exocrine: the vast majority of tumors of the pancreas arise in the exocrine part and these cancers look like pancreatic ducts under the microscope. These tumors are therefore called "ductal adenocarcinomas," or simply "adenocarcinoma," or even more simply "pancreatic cancer."
  • Endocrine: less commonly, tumors arise from the endocrine component of the pancreas and these endocrine tumors are called "pancreatic neuroendocrine tumors," or "islet cell tumors" for short.