Anatomy of the Pancreas
The pancreas is an organ that stretches partway across the abdomen, just below the stomach. Because its main functions are to aid digestion and produce hormones that control blood glucose levels, the pancreas is a focal point for understanding diabetes.
In addition to secreting certain enzymes that help you properly digest food, the pancreas manufactures hormones that regulate blood glucose—the fuel that provides the body's cells with energy. Scattered throughout the pancreas are tiny nests of cells known as islets of Langerhans; the majority of the cells are beta cells that produce and store the hormone insulin until needed. Also located in the islets are alpha cells, which make and store glucagon, a hormone that counteracts the effects of insulin.
After a meal, carbohydrates in foods are converted into glucose in the intestine and liver and enter the bloodstream. Beta cells sense the rising blood glucose levels and secrete insulin into the blood. Once in the bloodstream, insulin helps glucose enter the body's cells, where it can be "burned" by the liver and muscles for energy. Liver and muscles can also convert glucose to glycogen, a type of reserve form of energy that is stored there for future needs.When the body is working as it should, blood glucose levels quickly return to normal, and insulin secretion decreases.
A drop in blood glucose levels—for example, when one hasn't eaten for several hours—stimulates an opposite effect: alpha cells secrete glucagon into the blood, which converts stored glycogen back into energy- producing glucose.
Normally, the secretion of these hormones by the pancreas is perfectly balanced: Beta and alpha cells continuously monitor blood glucose levels and release insulin or glucagon as needed. In diabetes, this balance is thrown off because beta cells produce little or no insulin or the body's cells are resistant to insulin action—or often both. Glucose then fails to enter cells effectively and the fuel for energy remains stuck in the bloodstream. The result is persistently high blood glucose levels (hyperglycemia). Without treatment, hyperglycemia can lead to serious long-term complications, such as eye, kidney, and heart disease and damage to nerves.