The pancreas is both an exocrine gland and an endocrine gland, making it one of the few organs in the body that performs both roles. About 90% of its tissue is dedicated to exocrine function (producing digestive enzymes), while only 1 to 2% consists of endocrine tissue (releasing hormones into the bloodstream). The remaining tissue is connective tissue, blood vessels, and nerves.
Why It’s Called a “Dual” Gland
Glands fall into two broad categories based on how they deliver their products. Exocrine glands secrete substances through ducts to a specific destination, like sweat glands releasing sweat onto your skin. Endocrine glands release hormones directly into the bloodstream, where they travel to distant organs. The pancreas does both, which is why it’s sometimes called a heterocrine or mixed gland.
These two systems operate independently within the same organ but are physically intertwined. The hormone-producing cells sit in tiny clusters scattered throughout the much larger mass of enzyme-producing tissue, like small islands in a sea of digestive machinery.
The Exocrine Pancreas: Digestive Enzymes
The exocrine portion, making up roughly 90% of the organ, produces digestive enzymes and delivers them through a duct system into the first section of the small intestine. Your pancreas generates 2 to 3 liters of pancreatic juice per day, an impressive volume for an organ only about 6 inches long.
This juice contains several categories of enzymes, each targeting a different nutrient. Proteases like trypsin, chymotrypsin, and elastase break down proteins. Lipase breaks down fats. Amylase breaks down starches. Nucleases break down DNA and RNA from the food you eat. Many of these enzymes are stored in an inactive form inside the pancreas to prevent the organ from digesting itself. They only switch on once they reach the small intestine, where a specialized enzyme on the intestinal wall activates the first one (trypsin), which then activates the rest in a chain reaction.
The pancreatic juice also contains a high concentration of bicarbonate, the same compound found in baking soda. This serves a critical purpose: stomach acid would destroy the digestive enzymes and damage the intestinal lining if left unneutralized. The bicarbonate raises the pH of the mixture to around 8.2, creating the mildly alkaline environment the enzymes need to work.
The Endocrine Pancreas: Hormones and Blood Sugar
The endocrine portion consists of clusters of hormone-producing cells called the islets of Langerhans. Despite making up just 1 to 2% of the pancreas by mass, these clusters have an outsized role in keeping your body functioning. Human islets contain several distinct cell types, each producing a different hormone:
- Beta cells (about 60% of islet cells) produce insulin, which lowers blood sugar by helping cells absorb glucose and store it as glycogen.
- Alpha cells (about 30%) produce glucagon, which raises blood sugar by triggering the liver to release stored glucose and manufacture new glucose from amino acids and fats.
- Delta cells produce somatostatin, which helps regulate the release of both insulin and glucagon.
- PP cells produce pancreatic polypeptide, which influences appetite and digestive secretions.
- Epsilon cells produce ghrelin, a hunger-signaling hormone.
Insulin and glucagon work as a pair in a continuous feedback loop. When blood sugar rises after a meal, beta cells release insulin to bring it down. When blood sugar drops between meals or during exercise, alpha cells release glucagon to bring it back up. This back-and-forth keeps your blood glucose within a narrow, safe range throughout the day.
Where the Pancreas Sits in Your Body
The pancreas is an elongated organ that lies horizontally across your upper abdomen, tucked behind the stomach. It sits in a retroperitoneal position, meaning it’s behind the membrane that lines the abdominal cavity rather than hanging freely inside it. The wider end (the head) nestles into the C-shaped curve of the duodenum, and the narrower end (the tail) extends to the left toward the spleen.
This positioning matters because the head of the pancreas is right where the digestive duct empties into the small intestine, giving the exocrine enzymes a short, direct path to where they’re needed.
What Happens When Each Side Fails
Because the pancreas has two distinct functions, problems with one side produce very different symptoms than problems with the other. Damage to the endocrine tissue is most commonly associated with diabetes. In type 1 diabetes, the immune system destroys beta cells, eliminating insulin production. In type 2 diabetes, the beta cells gradually lose their effectiveness, and the broader communication network between islet cells and the rest of the pancreas deteriorates. Chronic pancreatitis can also destroy islet cells directly, producing a distinct form sometimes called type 3 diabetes.
Damage to the exocrine tissue causes exocrine pancreatic insufficiency, where the organ no longer produces enough digestive enzymes. This leads to poor nutrient absorption, particularly of fats, causing oily stools, weight loss, and nutritional deficiencies. This condition can be detected through a stool test measuring levels of a specific enzyme. Studies have found that 10 to 45% of young people with type 1 diabetes already show signs of reduced exocrine function, suggesting the two sides of the pancreas are more interconnected than they might appear.
That interconnection runs in both directions. Insulin has a direct growth-promoting effect on the exocrine cells surrounding the islets. When insulin production drops, the exocrine tissue can shrink and weaken. Conversely, chronic inflammation of the exocrine tissue (pancreatitis) can scar and destroy nearby islets, triggering diabetes. The two halves of this dual gland share a blood supply, nerve connections, and signaling pathways, so disease in one part frequently spills over into the other.