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the pancreas

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Anatomy

The pancreas is an organ located posterior to the stomach and in close association with the duodenum.

In humans, the pancreas is a small elongated organ in the abdomen located retroperitoneal. It is described as having a head, body and tail. The pancreatic head abuts the second part of the dudenum while the tail extends towards the spleen. The pancraetic duct runs the length of the pancreas and empties into the second part of the duodenum at the ampilla of Vater. the common bile duct commonly joins the pancreatic duct at or near this point.

It is supplied arterially by the pancreaticduodenal arteries, themselves branches of the superiour mesenteric artery. Venous drainage is via the pancraeticduodenal veins which end up in the portyal vein. the splenic veinpasses posterior to the pancreas but is said to not drain the pancreas itself. the portal vein is formed by the union of the super mesenteric vein and splenic vein posterior to the body 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).

function

The pancreas produces enzymes that break down all categories of digestible foods (exocrine pancreas) and secretes hormones that affect carbohydrate metabolism (endocrine pancreas)

Common Diseases of the Pancreas

When pancreas function is compromised, a number of possible health complications can arise. The location of the gland, buried as it is in the abdomen, makes it difficult to detect problems. Physical palpation of the gland is not possible, so blood tests and diagnostic imaging are often needed to diagnose pancreatic health difficulties. Health problems may include:

Pancreatitis is inflammation of the organ, and is often a source of pain. Pancreatitis may have a number of causes, and can be acute or chronic, hereditary or acquired. In some cases, pancreatitis can be fatal.

Pancreatic Cancer is the fifth leading cause of cancer deaths worldwide. The disease has a high mortality rate, and treatment options are, at present, limited. Diabetes and pancreatitis are considered to be risk factors.

Type 1 Diabetes occurs when insulin production either shuts down or is severely reduced. The body is then unable to maintain appropriate blood sugar levels.

Type 2 Diabetes occurs when insulin production is normal, but the body's cells no longer respond correctly to the hormone.

Cystic Fibrosis is a genetic disorder that causes the body to produce thick mucus that interferes with both respiratory function and the exocrine system. The mucus blocks the pancreas ducts, preventing digestive enzymes from reaching the small intestine. This results in insufficient digestion and malnutrition.

 

 
 

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exocrine and endocrine

exocrine

The pancreas is covered in a tissue capsule that partitions the gland into lobules. The bulk of the pancreas is composed of pancreatic exocrine cells, whose ducts are arranged in clusters called acini (singular acinus). The cells are filled with secretory granules containing the pre-cursor digestive enzymes (mainly trypsinogen, chymotrypsinogen, pancreaiic lipase and amylase) that are secreted into the lumen of the acinus. These granules are termed zymogen granules (zymogen referring to the inactive precursor enzymes).

Zymogen granules are localized to the subapical area of pancreatic acinar cells. After fusion with the apical membrane, they are flushed into the duodenum, where enterokinases (bound to enterocytes but facing the lumen of the duodenum) catalyze the activation of trypsinogen into trypsin. Trypsin, an endopeptidase, cleaves amino acids from chymotrypsinogen to produce an active endopeptidase, chymotrypsin. These in turn can 'chop up' polypeptides, released from stomach, into absorbable units. They also activate the other enzymes released. It is important to synthesize inactive enzymes in the pancreas to avoid autodegradation, which can lead to pancreatitis.

The pancreas is the main source of enzymes for digesting fats (lipids) 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 andsecretin, 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 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 potency of its enzyme contents, it is a very dangerous organ to injure and 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 the B (glucagon producing) cells, the a (insulin producing) cells, the delta (somatostatin producing) cells and a small number of F cells secreting Pancreatic polypeptide. The hormones produced by these cells have a critical role in regulating blood glucose levels in the fed and fasted states.

 

 

 

 

 

 

 

 

 

 

 

 

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