Pancreas

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For the song by "Weird Al" Yankovic, see Pancreas (song)

The pancreas is an organ in the digestive and endocrine system that serves two major functions: exocrine (producing pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin).

[edit] Anatomy

In humans, the pancreas is a 15-25 cm (6-10 inch) elongated organ in the abdomen located retroperitoneal. It is located posterior to the stomach and in close association with the duodenum.

It is often described as having three regions: a head, body and tail.

• The body of the pancreas lies at the level of L2 on the spine.
• The pancreatic head abuts the second part of the duodenum.
• The tail of the pancreas extends towards the spleen.

The pancreatic duct runs the length of the pancreas and empties into the second part of the duodenum at the ampulla of Vater. The common bile duct commonly joins the pancreatic duct at or near this point.

[edit] Arteries and veins

The pancreas is supplied arterially by the pancreaticoduodenal arteries:

• the superior mesenteric artery provides the inferior pancreaticoduodenal arteries
• 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).

[edit] Function

Under a microscope, when properly stained, it is easy to distinguish two different tissue types in the pancreas:<ref>Histology at BU 10404loa</ref>. These regions correspond to the main pancreatic functions:

[edit] 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:

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.

[edit] Exocrine

The pancreas is composed of pancreatic exocrine cells, whose ducts are arranged in clusters called acini (singular acinus). Pancreatic secretions are secreted into the lumen of the acinus, and then accumulate in intralobular ducts that drain to the main pancreatic duct, which drains directly into the duodenum.

Control of the exocrine function of the pancreas are via the hormones gastrin, cholecystokinin and secretin, which are hormones secreted by cells in the stomach and duodenum, in response to distension and/or food and which cause secretion of pancreatic juices.

There are two main classes of exocrine pancreatic secretions:

Pancreatic secretions from ductal cells contain bicarbonate ions and are alkaline in order to neutralize the acidic chyme that the stomach churns out.

The pancreas is also the main source of enzymes for digesting fats (lipids) and proteins. (The enzymes that digest polysaccharides, by contrast, are primarly produced by the walls of the intestines.)

The cells are filled with secretory granules containing the precursor digestive enzymes. The major proteases which the pancreas secretes are trypsinogen and chymotrypsinogen (and to a lesser degree, pancreatic lipase and pancreatic amylase.

It is important to synthesize inactive enzymes in the pancreas to avoid autodegradation, which can lead to pancreatitis. These granules are termed zymogen granules (the term "zymogen" referring to the inactive precursor enzymes). Trypsinogen is an inactivated forms of trypsin, and chymotrypsinogen is an inactivated form of chymotrypsin.

Once released in the intestine, the enzyme enterokinase present in the intestinal mucosa activates trypsinogen by cleaving it to form trypsin. The free trypsin then cleaves the rest of the trypsinogen and chymotrypsinogen to their active forms.

[edit] Edibility

Pancreas comes from the Greek pankreas (a combination of pan and kreas) which means 'all meat'.<ref>http://www.randomhouse.com/wotd/index.pperl?date=20010222 Review 2005-03-10</ref> Kreas in Homeric literature meant edible animal flesh. An example of one such food that can be made from the pancreas of a calf, lamb or pig is sweetbread.

[edit] Diseases of the pancreas

Due to the importance of its enzyme contents, injuring the pancreas is a very dangerous situation. A puncture of the pancreas tends to require careful medical intervention.

• Benign tumours
• Carcinoma of pancreas (pancreatic cancer)
• Cystic fibrosis
• Diabetes
• Exocrine pancreatic insufficiency
• Hemosuccus pancreaticus, or bleeding from or through the pancreatic duct
• Pancreatitis
  • Acute pancreatitis
  • Chronic pancreatitis
  • Hereditary pancreatitis
• Pancreatic pseudocyst

[edit] History

• The pancreas was discovered 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.

[edit] See also

• Artificial pancreas - a device currently under development that may be useful in patients with diabetes mellitus type 1
• Pancreas transplantation

[edit] Additional images

Accessory digestive system.	Digestive organs.	The celiac artery and its branches; the stomach has been raised and the peritoneum removed.	Lymphatics of stomach, etc. The stomach has been turned upward.
Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas.	The duodenum and pancreas.	The pancreatic duct.	Pancreas of a human embryo of five weeks.
Pancreas of a human embryo at end of sixth week.	Front of abdomen, showing surface markings for duodenum, pancreas, and kidneys.

[edit] References

<references/>

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