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The 'pancreas' is a gland organ in the digestive and endocrine systems of vertebrates6. It is both exocrine (secreting pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin, glucagon, and somatostatin). It is considered to be the most important intestinal gland.
Anatomy
In humans, the pancreas is a 15-25 cm (6-10 inch) elongated organ in the abdomen. It weighs between 65g - 75g. One of the organs behind the abdominal cavity, it is located posterior to the stomach and in close association with the duodenum.
It is often described as having four regions: a head, neck, body and tail.
★ The pancreatic head abuts the second part of the duodenum.
★ The pancreatic neck springs from the right upper portion of the front of the head.
★ The body of the pancreas lies at the level of L2 on the spine.
★ The tail of the pancreas extends towards the spleen.
The pancreatic duct (also called the duct of Wirsung2) runs the length of the pancreas and empties into the second part of the duodenum at the ampulla of Vater. The common bile duct usually joins the pancreatic duct at or near this point.
Many people also have a small accessory duct, the duct of Santorini, which extends from the main duct more upstream (towards the tail) to the duodenum, joining it more proximal than the ampulla of Vater.[2]
Blood supply
The pancreas is supplied arterially by the Pancreaticoduodenal arteries[1] and the splenic artery:
★ the splenic artery supplies the neck, body, and tail of the pancreas.
★ the superior mesenteric artery provides the inferior pancreaticoduodenal artery
★ the gastroduodenal artery provides the superior pancreaticoduodenal artery
Venous drainage is via the pancreaticoduodenal veins which end up in the portal vein. The splenic vein passes posterior to the pancreas but is said to not drain the pancreas itself. The portal vein is formed by the union of the superior mesenteric vein and splenic vein posterior to the neck of the pancreas. In some people (some books say 40% of people), the inferior mesenteric vein also joins with the splenic vein behind the pancreas (in others it simply joins with the superior mesenteric vein instead).
Nerves
The pancreas is innervated by the pancreatic plexus; a subdivision of the celiac plexus that accompanies pancreatic arteries.......
Function
Under a microscope, when properly stained, it is easy to distinguish two different tissue types in the pancreas.[1] These regions correspond to the main pancreatic functions:
| 'Appearance' | 'Region' | 'Function' |
| light staining circles (islets of Langerhans) | endocrine pancreas | secretes hormones that regulate blood glucose levels |
| darker surrounding tissue | exocrine pancreas | produces enzymes that break down digestible foods |
Endocrine
There are four main types of cells in the islets of Langerhans. They are relatively difficult to distinguish using standard staining techniques, but they can be classified by their secretion:
| 'Name of cells' | 'Endocrine product' | '% of islet cells' | 'Representative function' |
| beta cells | Insulin and Amylin | 50-80% | lower blood sugar |
| alpha cells | Glucagon | 15-20% | raise blood sugar |
| delta cells | Somatostatin | 3-10% | inhibit endocrine pancreas |
| PP cells | Pancreatic polypeptide | 1% | inhibit exocrine pancreas |
The islets are a compact collection of endocrine cells arranged in clusters and cords and are crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of endocrine cells in direct contact with vessels, and most endocrine cells are in direct contact with blood vessels, by either cytoplasmic processes or by direct apposition. According to the volume ''The Body,'' by Alan E. Nourse, in the Time-Life Science Library Series, the islets are "busily manufacturing their hormone and generally disregarding the pancreatic cells all around them, as though they were located in some completely different part of the body." (op. cit., p. 171.)
Exocrine
There are two main types of exocrine pancreatic cells, responsible for two main classes of secretions:
| 'Name of cells' | 'Exocrine secretion' | 'Primary signal' |
| Centroacinar cells | bicarbonate ions | Secretin |
| Basophilic cells | digestive enzymes (pancreatic amylase, Pancreatic lipase, trypsinogen, chymotrypsinogen, etc.) | CCK |
Diseases of the pancreas
Due to the importance of its enzyme contents, injury to the pancreas is potentially very dangerous. A puncture of the pancreas generally requires prompt and experienced medical intervention.
Diseases associated with the pancreas include:
Diabetes mellitus
Diabetes mellitus is a metabolic disorder characterized by hyperglycemia. All three forms of the disease are due to the inability of the beta cells of the pancreas to produce sufficient insulin.
Researchers at the Toronto Hospital for Sick Children injected capsaicin into NOD mice (Non-obese diabetic mice, a strain that is genetically predisposed to develop the equivalent of diabetes mellitus type 1) to kill the pancreatic sensory nerves. This treatment reduced the development of diabetes mellitus in these mice by 80%, suggesting a link between neuropeptides and the development of diabetes. When the researchers injected the pancreas of the diabetic mice with sensory neuropeptide (sP), they were cured of the diabetes for as long as 4 months. Also, insulin resistance (characteristic of diabetes mellitus type 2) was reduced.
Benign tumours
Like any other organ, the pancreas is susceptible to the growth of benign tumors. Benign tumors do not invade neighboring tissues, do not cause metastases, and usually do not return after surgical removal.
Pancreatic cancer
Pancreatic cancer is a malignant tumour within the pancreatic gland. Its prognosis is generally regarded as poor. The different types of pancreatic cancers include:
★ Tumors of the centroacinar cells.
★ Pancreatic Exocrine Tumors. Examples include:
★
★ Pancreatic adenocarcinoma. It represents about 95% of all pancreatic tumors. 75% to 96% of all pancreatic adenocarcinomas are ductal cell adenocarcinomas.
★
★ Other tumors of the exocrine pancreas, such as serous cystadenomas.
★ Pancreatic Endocrine Tumors (PET's), also known as Endocrine Pancreatic Tumors (EPT's), or Islet Cell Tumors. They are a type of Neuroendocrine tumors. PET's represent between 1 and 2% of all pancreatic tumors. Between 15 and 30% of all PET's are non-functioning, while 70 to 85% of them are functioning. Examples of functioning PET's include:
★
★ Gastrinoma, producing excessive gastrin and causing Zollinger-Ellison Syndrome (ZES)
★
★ Insulinoma, producing excessive insulin
★
★ Glucagonoma, producing excessive glucagon
★
★ Vasoactive intestinal peptideoma (VIPoma), producing excessive vasoactive intestinal peptide (VIP)
★
★ PPoma, producing excessive pancreatic polypeptide (often classed with non-functioning PETs)
★
★ Somatostatinoma, producing excessive somatostatin
★
★ Watery diarrhea, hypokalemia-achlorhydria (WDHA)
★
★ CRHoma, producing excessive corticotropin-releasing hormonse (CRH)
★
★ Calcitoninoma, producing excessive calcitonin
★
★ GHRHoma, producing excessive growth-hormone-releasing hormone (GHRH)
★
★ Neurotensinoma, producing excessive neurotensin
★
★ ACTHoma, producing excessive adrenocorticotropic hormone (ACTH)
★
★ GRFoma, producing excessive growth-hormone release factor (GRF)
★
★ Parathyroid hormone–related peptide tumor
Cystic fibrosis
Cystic fibrosis, also known as 'mucoviscidosis', is a hereditary disease that affects the entire body, causing progressive disability and early death. There is no cure for cystic fibrosis, and most affected individuals die young from lung failure. Cystic fibrosis is caused by a mutation in a gene called the cystic fibrosis transmembrane conductance regulator (CFTR). The product of this gene helps create sweat, digestive juices, and mucus. Although most people without CF have two working copies of the CFTR gene, only one is needed to prevent cystic fibrosis. Cystic fibrosis develops when neither gene works normally. Therefore, it is considered an autosomal recessive disease. The name ''cystic fibrosis'' refers to the characteristic 'fibrosis' (tissue scarring) and cyst formation within the pancreas. Cystic fibrosis causes irreversible damage to the pancreas, which often results in painful inflammation (pancreatitis).
Exocrine pancreatic insufficiency
Exocrine pancreatic insufficiency (EPI) is the inability to properly digest food due to a lack of digestive enzymes made by the pancreas. EPI is found in humans afflicted with cystic fibrosis. It is caused by a progressive loss of the pancreatic cells that make digestive enzymes. Chronic pancreatitis is the most common cause of EPI in humans. Loss of digestive enzymes leads to maldigestion and malabsorption of nutrients.
Hemosuccus pancreaticus
Hemosuccus pancreaticus, also known as pseudohematobilia or Wirsungorrhage, is a rare cause of hemorrhage in the gastrointestinal tract. It is caused by a bleeding source in the pancreas, pancreatic duct, or structures adjacent to the pancreas, such as the splenic artery, that bleed into the pancreatic duct. Patients with hemosuccus may develop symptoms of gastrointestinal hemorrhage, such as blood in the stools, maroon stools, or melena. They may also develop abdominal pain. Hemosuccus pancreaticus is associated with pancreatitis, pancreatic cancer and aneurysms of the splenic artery. Angiography may be used to treat hemosuccus pancreaticus, where the celiac axis is injected to determine the blood vessel that is bleeding, because embolization of the end vessel may terminate the hemorrhage. Alternatively, a distal pancreatectomy may be required to stop the hemorrhage.
Pancreatitis
Pancreatitis is inflammation of the pancreas. There are three forms of pancreatitis, which are different in causes and symptoms, and require different treatment:
★ Acute pancreatitis: A rapidly-onset inflammation of the pancreas.
★ Chronic pancreatitis: A long-standing inflammation of the pancreas.
★ Hereditary pancreatitis: A genetic abnormality that renders trypsinogen active within the pancreas, which in turn leads to digestion of the pancreas from the inside.
Pancreatic pseudocyst
A pancreatic pseudocyst is a circumscribed collection of fluid rich in amylase and other pancreatic enzymes, blood and necrotic tissue, typically located in the lesser sac.
History
The pancreas was first identified by Herophilus (335-280 BC), a Greek anatomist and surgeon. Only a few hundred years later, Ruphos, another Greek anatomist, gave the pancreas its name. The term "pancreas" is derived from the Greek ''pan'', "all", and ''kreas'', "flesh", probably referring to the organ's homogeneous appearance.[5]
Pancreas as a food
Pancreases (specifically calf and lamb pancreases) are used in some meals often going by the name ''stomach sweetbreads''.[6]
Pop culture references
Heywood Banks, who performs regularly on the Bob & Tom Show, recorded a song titled "The Pancreas," composed of doggerel verses that rather accurately, if facetiously, decribe the function of the pancreas. The lyrics include "Let's all sing a tribute to the pancreas...hey pancreas, have a nice day!"
Satiric singer "Weird Al" Yankovic has recently produced a song titled "Pancreas." It includes many lyrics about the functions of the organ as well as the names of various chemicals it produces, concluding, "I love my pancreas!" The song can be found on his 2006 album "Straight Outta Lynwood."
In The Fairly Odd Parents, when Cosmo was Kenny Kidney, Wanda was Penny Pancreas. The residents made references that the pancreas isn't a vital organ.
Italian Opera singer Luciano Pavarotti died of pancreatic cancer at the age of 71 on the 6th of September 2007.
Additional images
References
1.
2. Cutler, Anne G., et al., eds. Stedman's Medical Dictionary. Baltimore: The William and Wilkins Company, 1976 ed.
3.
4.
5. Pancreas
6. New Standard Encyclopedia, 1988. Volume P Page 68
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