Pancreas
The pancreas is an organ in the digestive system that serves two major functions:
*
exocrine - producing pancreatic juice containing
digestive enzymes.
*
endocrine - producing several important hormones, including
insulin.
Encyclopedia
The
pancreas is an organ in the digestive system that serves two major functions:
...
enzymes.
Anatomy
The pancreas is located posterior to the stomach and in close association with the duodenum.
In humans, the pancreas is a 15-25 cm elongated organ in the abdomen located retroperitoneal. It is often described as having three regions: a head, body and tail. The pancreatic head abuts the second part of the duodenum while the tail 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.
The pancreas is supplied arterially by the pancreaticoduodenal arteries, themselves branches of the superior mesenteric artery or of the hepatic artery . The superior mesenteric artery provides the inferior pancreaticoduodenal arteries while 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 body of the pancreas. In some people , the inferior mesenteric vein also joins with the splenic vein behind the pancreas .
Function
The pancreas produces enzymes that break down all categories of digestible foods and secretes hormones that affect carbohydrate metabolism .
Exocrine
The pancreas is composed of pancreatic exocrine cells, whose ducts are arranged in clusters called
acini . The cells are filled with secretory granules containing the precursor digestive enzymes that are secreted into the lumen of the acinus. These granules are termed zymogen granules . It is important to synthesize inactive enzymes in the pancreas to avoid autodegradation, which can lead to pancreatitis.
The pancreas is near the liver, and is the main source of enzymes for digesting fats and proteins - the intestinal walls have enzymes that will digest polysaccharides. Pancreatic secretions from ductal cells contain bicarbonate ions and are alkaline in order to neutralize the acidic chyme that the stomach churns out.
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.
The two major proteases which the pancreas secretes are trypsinogen and chymotrypsinogen. These zymogens are inactivated forms of trypsin and
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.
Pancreatic secretions accumulate in intralobular ducts that drain to the main pancreatic duct, which drains directly into the duodenum.
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.
Endocrine
Scattered amongst the acini are the endocrine cells of the pancreas, in groups called the
islets of Langerhans. They are:
- Insulin-producing beta cells
- Glucagon-releasing alpha cells
- Somatostatin-producing delta cells
- Pancreatic polypeptide-containing PP cells 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.
Edibility
Pancreas comes from the Greek
pankreas which means 'all meat'.
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.
The ancient Egyptians also used to eat the liver of dogs, and considered them a delicacy.
Diseases of the pancreas
History
- The pancreas was discovered by Herophilus , a Greek anatomist and surgeon. Only a few hundred years later, Ruphos, another Greek anatomist, gave the pancreas its name.
- "Weird Al" Yankovic dedicated an entire song to the pancreas in 2006 with the release of his album, Straight Outta Lynwood.
See also
References
http://www.randomhouse.com/wotd/index.pperl?date=20010222 Review 2005-03-10
