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The pancreas (plural pancreases, or pancreata) is an organ of the Digestion and endocrine system of . In humans, it is located in the abdominal cavity behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e., it has both an endocrine and a digestive exocrine function. Ninety-nine percent of the pancreas is exocrine and 1% is endocrine. (2025). 9780128122006 ISBN 9780128122006 As an endocrine gland, it functions mostly to regulate blood sugar levels, secreting the insulin, glucagon, somatostatin and pancreatic polypeptide. As a part of the digestive system, it functions as an exocrine gland secreting pancreatic juice into the duodenum through the pancreatic duct. This juice contains bicarbonate, which neutralizes acid entering the duodenum from the stomach; and , which break down carbohydrates, and lipids in food entering the duodenum from the stomach.
Inflammation of the pancreas is known as pancreatitis, with common causes including chronic alcohol use and . Because of its role in the regulation of blood sugar, the pancreas is also a key organ in diabetes. Pancreatic cancer can arise following chronic pancreatitis or due to other reasons, and carries a very poor prognosis, as it is often only identified after it has spread to other areas of the body.
The word pancreas comes from the Greek language πᾶν (pân, "all") & κρέας (kréas, "flesh"). The function of the pancreas in diabetes has been known since at least 1889, with its role in insulin production identified in 1921.
Anatomically, the pancreas is divided into a head, neck, body, and tail. The pancreas stretches from the inner curvature of the duodenum, where the head surrounds two : the superior mesenteric artery and vein. The longest part of the pancreas, the body, stretches across behind the stomach, and the tail of the pancreas ends adjacent to the spleen.
Two ducts, the main pancreatic duct and a smaller accessory pancreatic duct run through the body of the pancreas. The main pancreatic duct joins with the common bile duct forming a small ballooning called the ampulla of Vater (hepatopancreatic ampulla). This ampulla is surrounded by a muscle, the sphincter of Oddi. This ampulla opens into the descending part of the duodenum. The opening of the common bile duct into Pancreatic duct is controlled by sphincter of Boyden. The accessory pancreatic duct opens into duodenum with separate openings located above the opening of the Pancreatic duct.
The neck of the pancreas separates the head of the pancreas, located in the curvature of the duodenum, from the body. The neck is about wide, and sits in front of where the portal vein is formed. The neck lies mostly behind the pylorus of the stomach, and is covered with peritoneum. The anterior superior pancreaticoduodenal artery travels in front of the neck of the pancreas.
The body is the largest part of the pancreas, and mostly lies behind the stomach, tapering along its length. The peritoneum sits on top of the body of the pancreas, and the transverse colon in front of the peritoneum. Behind the pancreas are several blood vessels, including the aorta, the splenic vein, and the left renal vein, as well as the beginning of the superior mesenteric artery. Below the body of the pancreas sits some of the small intestine, specifically the last part of the duodenum and the jejunum to which it connects, as well as the suspensory ligament of the duodenum which falls between these two. In front of the pancreas sits the transverse colon.
The pancreas narrows towards the tail, which sits near to the spleen. It is usually between long, and sits between the layers of the ligament between the spleen and the left kidney. The splenic artery and splenic vein pass behind the body and tail of the pancreas.
The body and neck of the pancreas drain into the splenic vein, which sits behind the pancreas. The head drains into, and wraps around, the superior mesenteric and , via the pancreaticoduodenal veins.
The pancreas drains into lymphatic vessels that travel alongside its artery, and has a rich lymphatic supply. The of the body and tail drain into splenic lymph nodes, and eventually into lymph nodes that lie in front of the aorta, between the coeliac and superior mesenteric arteries. The lymphatic vessels of the head and neck drain into intermediate lymphatic vessels around the pancreaticoduodenal, mesenteric and hepatic arteries, and from there into the lymph nodes that lie in front of the aorta.
The majority of pancreatic Parenchyma has a digestive role. The cells with this role form clusters (acini) around small ducts, and are arranged in lobes that have thin fibrous tissue walls. The cells of each acinus secrete inactive digestive enzymes called into the small intercalated ducts which they surround. In each acinus, the cells are pyramid-shaped and situated around the intercalated ducts, with the Cell nucleus resting on the basement membrane, a large endoplasmic reticulum, and a number of zymogen granules visible within the cytoplasm. The intercalated ducts drain into larger intralobular ducts within the lobule, and finally interlobular ducts. The ducts are lined by a single layer of column-shaped cells. There is more than one layer of cells as the diameter of the ducts increases.
The tissues with an endocrine role within the pancreas exist as clusters of cells called pancreatic islets (also called islets of Paul Langerhans) that are distributed throughout the pancreas. Pancreatic islets contain , , and , each of which releases a different hormone. These cells have characteristic positions, with alpha cells (secreting glucagon) tending to be situated around the periphery of the islet, and beta cells (secreting insulin) more numerous and found throughout the islet. Enterochromaffin cells are also scattered throughout the islets. Islets are composed of up to 3,000 secretory cells, and contain several small arterioles to receive blood, and venules that allow the hormones secreted by the cells to enter the systemic circulation.
The definitive pancreas results from rotation of the ventral bud and the fusion of the two buds. During development, the duodenum rotates to the right, and the ventral bud rotates with it, moving to a position that becomes more dorsal. Upon reaching its final destination, the ventral pancreatic bud is below the larger dorsal bud, and eventually fuses with it. At this point of fusion, the main ducts of the ventral and dorsal pancreatic buds fuse, forming the main pancreatic duct. Usually, the duct of the dorsal bud regresses, leaving the main pancreatic duct.
The cells of the exocrine pancreas differentiate through molecules that induce differentiation including follistatin, fibroblast growth factors, and activation of the Notch receptor system. Development of the exocrine acini progresses through three successive stages. These are the predifferentiated, protodifferentiated, and differentiated stages, which correspond to undetectable, low, and high levels of digestive enzyme activity, respectively.
Pancreatic progenitor cells differentiate into endocrine islet cells under the influence of neurogenins and ISL1, but only in the absence of notch receptor signaling. Under the direction of a Pax gene, the endocrine precursor cells differentiate to form alpha and gamma cells. Under the direction of Pax-6, the endocrine precursor cells differentiate to form beta and delta cells. The pancreatic islets form as the endocrine cells migrate from the duct system to form small clusters around capillary. This occurs around the third month of development, and insulin and glucagon can be detected in the human fetal circulation by the fourth or fifth month of development.
]] Cells within the pancreas help to maintain blood glucose levels (homeostasis). The cells that do this are located within the pancreatic islets that are present throughout the pancreas. The following processes take place with blood glucose levels:
in the islet also secrete somatostatin which decreases the release of insulin and glucagon.
Glucagon acts to increase glucose levels by promoting the gluconeogenesis and the glycogenolysis to glucose in the liver. It also decreases the uptake of glucose in fat and muscle. Glucagon release is stimulated by low blood glucose or insulin levels, and during exercise. Insulin acts to decrease blood glucose levels by facilitating uptake by cells (particularly skeletal muscle), and promoting its use in the creation of proteins, fats and carbohydrates. Insulin is initially created as a precursor form called preproinsulin. This is converted to proinsulin and cleaved by C-peptide to insulin which is then stored in granules in beta cells. Glucose is taken into the beta cells and degraded. The end effect of this is to cause depolarisation of the cell membrane which stimulates the release of the insulin.
The main factor influencing the secretion of insulin and glucagon are the levels of glucose in blood plasma. (2025). 9781260122404 ISBN 9781260122404 Low blood sugar stimulates glucagon release, and high blood sugar stimulates insulin release. Other factors also influence the secretion of these hormones. Some , that are byproducts of the digestion of protein, stimulate insulin and glucagon release. Somatostatin acts as an inhibitor of both insulin and glucagon. The autonomic nervous system also plays a role. Activation of Beta-2 receptors of the sympathetic nervous system by secreted from sympathetic nerves stimulates secretion of insulin and glucagon, (2025). 9781455770168, Elsevier. ISBN 9781455770168 whereas activation of Alpha-1 receptors inhibits secretion. M3 receptors of the parasympathetic nervous system act when stimulated by the right vagus nerve to stimulate release of insulin from beta cells.
The cells in each acinus are filled with granules containing the digestive enzymes. These are secreted in an inactive form termed or proenzymes. When released into the duodenum, they are activated by the enzyme enterokinase present in the lining of the duodenum. The proenzymes are cleaved, creating a cascade of activating enzymes.
These enzymes are secreted in a fluid rich in bicarbonate. Bicarbonate helps maintain an alkaline pH for the fluid, a pH in which most of the enzymes act most efficiently, and also helps to neutralise the stomach acids that enter the duodenum. Secretion is influenced by hormones including secretin, cholecystokinin, and VIP, as well as acetylcholine stimulation from the vagus nerve. Secretin is released from the which form part of the lining of the duodenum in response to stimulation by gastric acid. Along with VIP, it increases the secretion of enzymes and bicarbonate. Cholecystokinin is released from of the lining of the duodenum and jejunum mostly in response to long chain fatty acids, and increases the effects of secretin. At a cellular level, bicarbonate is secreted from centroacinar and ductal cells through a sodium and bicarbonate cotransporter that acts because of membrane depolarisation caused by the cystic fibrosis transmembrane conductance regulator. Secretin and VIP act to increase the opening of the cystic fibrosis transmembrane conductance regulator, which leads to more membrane depolarisation and more secretion of bicarbonate.
A variety of mechanisms act to ensure that the digestive action of the pancreas does not act to digest pancreatic tissue itself. These include the secretion of inactive enzymes (zymogens), the secretion of the protective enzyme trypsin inhibitor, which inactivates trypsin, the changes in pH that occur with bicarbonate secretion that stimulate digestion only when the pancreas is stimulated, and the fact that the low calcium within cells causes inactivation of trypsin.
In pancreatitis, enzymes of the exocrine pancreas damage the structure and tissue of the pancreas. Detection of some of these enzymes, such as amylase and lipase in the blood, along with symptoms and findings on medical imaging such as ultrasound or a CT scan, are often used to indicate that a person has pancreatitis. Pancreatitis is often managed medically with analgesic, and monitoring to prevent or manage shock, and management of any identified underlying causes. This may include removal of gallstones, lowering of blood triglyceride or glucose levels, the use of for autoimmune pancreatitis, and the cessation of any medication triggers.
Chronic pancreatitis refers to the development of pancreatitis over time. It shares many similar causes, with the most common being chronic alcohol use, with other causes including recurrent acute episodes and cystic fibrosis. Abdominal pain, characteristically relieved by sitting forward or drinking alcohol, is the most common symptom. When the digestive function of the pancreas is severely affected, this may lead to problems with fat digestion and the development of steatorrhoea; when the endocrine function is affected, this may lead to diabetes. Chronic pancreatitis is investigated in a similar way to acute pancreatitis. In addition to management of pain and nausea, and management of any identified causes (which may include alcohol cessation), because of the digestive role of the pancreas, enzyme replacement may be needed to prevent malabsorption.
Pancreatic adenocarcinoma is the most common form of pancreatic cancer, and is cancer arising from the exocrine digestive part of the pancreas. Most occur in the head of the pancreas. Symptoms tend to arise late in the course of the cancer, when it causes abdominal pain, weight loss, or yellowing of the skin (jaundice). Jaundice occurs when the outflow of bile is blocked by the cancer. Other less common symptoms include nausea, vomiting, pancreatitis, diabetes or recurrent venous thrombosis. Pancreatic cancer is usually diagnosed by medical imaging in the form of an ultrasound or CT scan with contrast enhancement. An endoscopic ultrasound may be used if a tumour is being considered for surgical removal, and biopsy guided by ERCP or ultrasound can be used to confirm an uncertain diagnosis.
Because of the late development of symptoms, most cancer presents at an advanced Cancer staging. Only 10 to 15% of tumours are suitable for surgical resection. , when chemotherapy is given the FOLFIRINOX regimen containing fluorouracil, irinotecan, oxaliplatin and leucovorin has been shown to extend survival beyond traditional gemcitabine regimens. For the most part, treatment is palliative, focus on the management of symptoms that develop. This may include management of itch, a choledochojejunostomy or the insertion of stents with ERCP to facilitate the drainage of bile, and medications to help control pain. In the United States pancreatic cancer is the fourth most common cause of deaths due to cancer. The disease occurs more often in the developed world, which had 68% of new cases in 2012.
There are several types of pancreatic cancer, involving both the endocrine and exocrine tissue. The many types of pancreatic endocrine tumors are all uncommon or rare, and have varied outlooks. However the incidence of these cancers has been rising sharply; it is not clear to what extent this reflects increased detection, especially through medical imaging, of tumors that would be very slow to develop. (largely benign) and are the most common types. For those with neuroendocrine cancers the number alive after five years is much better at 65%, varying considerably with type.
A solid pseudopapillary tumour is a low-grade malignant tumour of the pancreas of papillary architecture that typically afflicts young women.
The way the tissue of the pancreas has been viewed has also changed. Previously, it was viewed using simple staining methods such as H&E stains. Now, immunohistochemistry can be used to more easily differentiate cell types. This involves visible antibodies to the products of certain cell types, and helps identify with greater ease cell types such as alpha and beta cells.
In teleost fish, and a few other species (such as ), there is no discrete pancreas at all, with pancreatic tissue being distributed diffusely across the mesentery and even within other nearby organs, such as the liver or spleen. In a few teleost species, the endocrine tissue has fused to form a distinct gland within the abdominal cavity, but otherwise it is distributed among the exocrine components. The most primitive arrangement, however, appears to be that of and lungfish, in which pancreatic tissue is found as a number of discrete nodules within the wall of the gut itself, with the exocrine portions being little different from other glandular structures of the intestine.
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(2025). 9789283204299, World Health Organization. ISBN 9789283204299 Pancreatic adenocarcinoma typically has poor outcomes with the average percentage alive for at least one and five years after diagnosis being 25% and 5% respectively. In localized disease where the cancer is small (< 2 cm) the number alive at five years is approximately 20%.
Diabetes mellitus
Type 1 diabetes
Diabetes mellitus type 1 is a chronic autoimmune disease in which the immune system attacks the insulin-secreting beta cells of the pancreas. (2025). 9781260122404, McGraw-Hill Education. ISBN 9781260122404 Insulin is needed to keep blood sugar levels within optimal ranges, and its lack can lead to hyperglycemia. As an untreated chronic condition, complications including accelerated vascular disease, diabetic retinopathy, kidney disease and neuropathy can result. In addition, if there is not enough insulin for glucose to be used within cells, the medical emergency diabetic ketoacidosis, which is often the first symptom that a person with type 1 diabetes may have, can result. Type 1 diabetes can develop at any age but is most often diagnosed before age 40. For people living with type 1 diabetes, insulin injections are critical for survival. An experimental procedure to treat type 1 diabetes is pancreas transplantation or isolated transplantation of islet cells to supply a person with functioning beta cells.
Type 2 diabetes
Diabetes mellitus type 2 is the most common form of diabetes. The causes for high blood sugar in this form of diabetes usually are a combination of insulin resistance and impaired insulin secretion, with both genetic and environmental factors playing a role in the development of the disease. Over time, pancreatic beta cells may become "exhausted" and less functional. The management of type 2 diabetes involves a combination of lifestyle measures, medications if required and potentially insulin.
With relevance to the pancreas, several medications act to enhance the secretion of insulin from beta cells, particularly , which act directly on beta cells; incretins which replicate the action of the hormones glucagon-like peptide 1, increasing the secretion of insulin from beta cells after meals, and are more resistant to breakdown; and DPP-4 inhibitors, which slow the breakdown of incretins.
Removal
It is possible for a person to live without a pancreas, provided that the person takes insulin for proper regulation of blood glucose concentration and pancreatic enzyme supplements to aid digestion.
History
The pancreas was first identified by Herophilus (335–280 BC), a Greeks anatomist and surgery. (2025). 9781461505556, Springer Science & Business Media. ISBN 9781461505556 A few hundred years later, Rufus of Ephesus, another Greek anatomist, gave the pancreas its name. Etymologically, the term "pancreas", a modern Latin adaptation of Greek language πάγκρεας, πᾶν, originally means sweetbread, although literally meaning all-flesh, presumably because of its fleshy consistency. It was only in 1889 when Oskar Minkowski discovered that removing the pancreas from a dog caused it to become diabetic. Insulin was later isolated from pancreatic islets by Frederick Banting and Charles Best in 1921.
Other animals
Pancreatic tissue is present in all , but its precise form and arrangement varies widely. There may be up to three separate pancreases, two of which arise from the pancreatic bud, and the other dorsally. In most species (including humans), these "fuse" in the adult, but there are several exceptions. Even when a single pancreas is present, two or three pancreatic ducts may persist, each draining separately into the duodenum (or equivalent part of the foregut). , for example, typically have three such ducts. (1977). 9780039102845, Holt-Saunders International. ISBN 9780039102845
Cuisine
The pancreas of veal ( ris de veau) or lamb ( ris d'agneau), and, less commonly, of beef or pork, are used as food under the culinary name of sweetbread. Oxford Companion to Food; Oxford English Dictionary (2025). 9780747560463, Bloomsbury. ISBN 9780747560463
Bibliography
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(2025). 9780071802154, McGraw-Hill Professional. ISBN 9780071802154
(2025). 9780702070280, Elsevier. ISBN 9780702070280
(2025). 9780808923718, Churchill Livingstone. ISBN 9780808923718
(2025). 9780702052309 ISBN 9780702052309
(2025). 9780702047473, Elsevier. ISBN 9780702047473
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