The pancreas is an endocrine as well as an exocrine gland which makes it unique among other organs. The pancreas is located retroperitoneally and is connected with the duodenum using the ampulla of vater, which is an opening that permits the secretions of the exocrine pancreas and bile secretions to enter the duodenum.
In cancer of the head of the pancreas this opening is blocked which renders a retention of bile secretion in the gallbladder. Thus predisposing to jaundice or yellowing of the skin color.
The exocrine secretions of the pancreas are mostly enzymes which participate in the digestion of food in the stomach. The pancreas secretes an enzyme which is called amylase. This enzyme participates in the digestion of carbohydrates that are present in the intestine.
Amylase is also secreted partially in the mouth by the salivary glands. Thus in pancreatic failure in which amylase secretion is impaired in the pancreas it is compensated by the secretion of the salivary glands.
The exocrine pancreas secretes in addition to amylase enzyme two other types of enzymes that specialize in the digestion of lipids and proteins. Proteins are digested using pancreatic enzymes that are specific for different types of amino acids cleavage.
These enzymes are trypsin and chymotrypsin in addition to another enzyme that is called carboxypeptidase. Each of these enzymes is specific for certain types of amino acids to be cleaved from the peptide bond. Proteinases are also secreted in the stomach in the form of an enzyme that is called pepsin. This enzyme is specific for proteins.
In pancreatic insufficiency or failure in which proteinases are lacking from the pancreatic juice the digestion of proteins is partially compensated in the stomach by the action of the enzyme pepsin on the proteins found in the stomach.
Lipids are also digested in the intestine using an enzyme that is called lipase. This enzyme is specific for lipids only. The secretion of lipase is specific only to pancreatic tissue and no other tissue secretes this type of enzyme.
Its deficiency as occurs in pancreatic insufficiency is not compensated for by other glands secretion. Therefore there are distinct clinical symptoms that are associated with pancreatic failure due to the lack of secretion of lipases in the pancreatic juice.
These symptoms include the presence of fat in the stool in addition to weight loss due to the lack of nutrients as a result of maldigestion. Secretions of the pancreas contain bicarbonate ions. Therefore its secretion is basic so that it can neutralize the acidic food in the stomach.
Usually the enzymes that are secreted by the pancreas are secreted in inactive form. They are activated in the duodenum by cleaving a certain number of amino acids from its structure.
In certain conditions such as reflux of duodenal enzymes to the pancreatic duct as a result of obstruction in the ampulla of vater in cancer of the head of the pancreas can lead to reflux of these enzymes into the pancreas itself. Thus leading to autodigestion to the pancreatic tissue. This leads in turn to destruction of pancreatic tissue and pancreatic failure.