A gland situated behind the lower part of the stomach. The head of the pancreas occupies the bend formed by the DUODENUM whilst the body extends to the left, ending in the tail which rests against the SPLEEN. A duct runs through the whole gland from left to right, joined by many small branches in its course, and, leaving the head of the gland, unites with the bile duct from the liver to open into the side of the small intestine about 7.5–10 cm (3–4 inches) below the outlet of the stomach.
Scattered through the pancreas are collections of cells known as the ISLETS OF LANGERHANS, of which there are around a million in a normal individual. These do not communicate with the duct of the gland, and the internal secretion of the pancreas – INSULIN – is formed by these cells and absorbed directly into the blood.
The most obvious function of the pancreas is the formation of the pancreatic juice, which is poured into the small intestine after the partially digested food has left the stomach. This is the most important of the digestive juices, is alkaline in reaction, and contains (in addition to various salts) four enzymes (see ENZYME) – TRYPSIN and CHYMOTRYPSIN, which digest proteins; AMYLASE, which converts starchy foods into the disaccharide maltose; and LIPASE, which breaks up fats. (See also DIGESTION.)
Inadequate production of insulin by the islets of Langerhans leads to the condition known as DIABETES MELLITUS. In addition to insulin, another hormone is produced by the pancreas: this is glucagon, which has the opposite effect to insulin and raises the blood sugar by promoting the breakdown of liver glycogen.