The pancreas is a long, lobe-like gland which is responsible for secreting the hormone insulin and an alkaline fluid which aids in digestion. Insulin is important in the body's utilization of blood sugar and lack of this hormone leads to diabetes mellitus. The digestive fluid is secreted directly into the duodenum, just below the stomach in the digestive tract.
The pancreas lies just behind the lower part of the stomach. It is the second largest gland in the body and is both an endocrine and an exocrine gland. Its exocrine function is to produce digestive juices (pancreatic juices) and release them through a tube, the pancreatic duct, to the intestine. The endocrine function of the pancreas is controlling the amount of sugar in the blood. The cells that control blood sugar levels are called islands of Langerhans. These islands are microscopic clumps of cells scattered throughout the pancreatic tissue among the other pancreatic cells but are concentrated somewhat in the tail of the pancreas.
There are two kinds of cells in the islands: alpha and beta. The alpha cells secrete a hormone called glucagon and the beta cells secrete insulin. Insulin and glucagon work as a check and balance system regulating the body's blood sugar level. Glucogon accelerates the process of liver glycogenesis (a chemical process by which the glucose stored in the liver cells in the form of glycogen is converted to glucose. This glucose then leaves the liver cells and enters the blood).
This process tends to increase the concentration of glucose in the blood. Insulin is an antigen to glucagon. It decreases the amount of blood glucose concentration. Insulin decreases blood glucose by accelerating its movement out of the blood, through cell membranes, and into cells. As glucose enters the cells at a faster rate, the cells increase their metabolism of glucose. All sugary and starchy foods, such as bread, potatoes, and cakes, are broken down into glucose. In this form they can be absorbed by every cell in the body, including the cells in the liver, one of whose major roles is to store sugar.
Cells absorb glucose and burn it in structures called mitochondria, using the energy it contains and producing carbon dioxide and water as byproducts. This burning up process is the body's principle source of energy. It cannot take place without insulin. Diabetes occurs when the pancreas fails to secrete enough insulin and so fails to regulate the glucose concentration in the blood. The normal glucose level for an average adult is about 80 to 120 milligrams of glucose in every 100 milliliters of blood. If the islands of Langerhans secrete too little insulin an excess of glucose develops, a characteristic of diabetes mellitus the most common disorder of the endocrine system.