Structure and Functions (Magill’s Medical Guide, Sixth Edition)
The pancreas is an organ about 15 to 18 centimeters long and weighing 100 grams that is located in the abdominal cavity. The head of the organ is situated in the loop of the small intestine that forms at the site where the small intestine joins the stomach. The pancreas is enclosed in a thin connective tissue capsule. As an accessory gland of the digestive system, the pancreas is an exocrine gland. Scattered within the tissue of this exocrine gland, however, are small distinct regions known as the islets of Langerhans, which are a part of the endocrine system. The exocrine portion composes by far the greatest mass of tissue. For example, in the guinea pig about 82 percent of pancreatic cells are exocrine cells, while the endocrine portion is about 2 percent. The remaining cells are associated with the duct system and the blood vessels.
The exocrine pancreas is an arrangement of tubules that continue to branch until they form very fine ducts called the intercalated ducts. Along the edges of the intercalated ducts are the acinar cells. These cells produce the pancreatic juices that aid in the digestion of food in the small intestine and help neutralize the contents of the small intestine. The products drain from the ducts into the main collecting duct, which joins the common bile duct and empties into the duodenum.
The islets of Langerhans, as is the case with all endocrine glands, have a well-developed blood...
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Disorders and Diseases (Magill’s Medical Guide, Sixth Edition)
Diseases of the pancreas can be divided into two basic categories: diseases of the exocrine cells of the organ and those diseases that effect the function of the endocrine portion, the islets of Langerhans. The exocrine cells of the pancreas can be affected by various conditions, including acute pancreatitis, chronic pancreatitis, cystic fibrosis, and carcinoma of the pancreas. Also, because the pancreas is a gland and glandular organs typically have a large blood supply, it is at risk of injury any time that circulation is impaired. The islets of Langerhans may be affected by diabetes mellitus.
Inflammation of the pancreas (pancreatitis) can be either acute or chronic. While some cases are mild, it is considered a serious disease and has a high mortality rate. Although the acute form is more serious, patients with chronic pancreatitis may suffer from acute episodes.
Acute pancreatitis may result from obstruction of the pancreatic duct (possibly by gallstones from the gallbladder or by mucous plugs, as in cystic fibrosis), bile reflux, acute intoxication by alcohol, shock, infection by the mumps virus, hypothermia, or trauma. The diagnosis, pathology, and prognosis are the same regardless of the cause.
The onset of the disease is usually quite sudden, with severe pain in the abdomen, nausea, and vomiting. Diagnosis is made by the presence of amylase in the blood serum. Amylase is an enzyme produced by the...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Since the pancreas is a vital organ, any disease or injury to it will have serious consequences. Problems with the pancreas may be magnified because the diseases associated with the exocrine portion of the gland are not easily detected. In acute cases of pancreatitis, the onset is sudden and requires immediate treatment to control the extent of the disease. Even when the disease is treated early, many patients die. Surgery is complicated by the inflammation and hemorrhaging that may have previously occurred.
Chronic pancreatitis and cancer of the pancreas are even more difficult to diagnose since many of the symptoms are common to other ailments and may not even be present until the disease has progressed to an acute stage. The chronic condition is complicated because the body cannot absorb nutrients and vitamins. By the time that the diagnosis has occurred, the patient is weakened by the loss of weight and muscular wasting from malnutrition.
Diabetes presents its own unique set of problems. In type 1 diabetes, the patient is often unable to follow the prescribed diet and must continually monitor his or her glucose levels to ensure that the insulin doses are appropriate. Assuming that the patient is able to follow the diet and takes the medication as prescribed, there will still be complications—particularly of the cardiovascular system—that may include renal damage.
Many advances have occurred...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Goodman, H. Maurice. Basic Medical Endocrinology. 4th ed. Boston: Academic Press/Elsevier, 2009. Contains good background information regarding endocrinology. Covers the endocrine activity of the pancreas and gives a thorough discussion of the physiological role of insulin and the other pancreatic hormones.
Howard, John M., and Walter Hess. History of the Pancreas: Mysteries of a Hidden Organ. New York: Kluwer Academic, 2002. A unique examination of the pancreas and its historical role in the science of medicine. Gives anecdotal vignettes of the researchers who have worked on this organ and details such events as the discovery of the islets of Langerhans and of insulin, gastrin, and their tumors.
Marieb, Elaine N. Essentials of Human Anatomy and Physiology. 9th ed. San Francisco: Pearson/Benjamin Cummings, 2009. This introductory anatomy and physiology textbook, easily accessible to those with little science background, is richly illustrated with diagrams and photographs that help to illuminate body systems and processes.
O’Reilly, Eileen, and Joanne Frankel Kelvin. One Hundred Questions and Answers About Pancreatic Cancer. 2d ed. Sudbury, Mass.: Jones and Bartlett, 2010. Gives both a doctor’s and patient’s points of view and covers treatment options, post-treatment quality of life, and sources of support.
Pizer, H. F. Organ Transplants: A Patient’s...
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Pancreas (Encyclopedia of Nursing & Allied Health)
The pancreas is an organ important in digestion and blood sugar regulation. It is considered to be part of the gastrointestinal system. The pancreas produces digestive enzymes to be released into the small intestine to aid in reducing food particles to basic elements that can be absorbed by the intestine and used by the body. It has another very different function in that it forms insulin, glucagon and other hormones to be sent into the bloodstream to regulate blood sugar levels and other activities throughout the body.
The pancreas is a pear-shaped organ about 6 in (15 cm) long located in the middle and back portion of the abdomen. It is connected to the first part of the small intestine, the duodenum, and lies behind the stomach. The pancreas is made up of glandular tissue, or cells that form substances to be secreted outside of the organ. Glandular tissues can be categorized as endocrine (secreting directly into the bloodstream or lymph) or exocrine (secreting into another organ). The pancreas is both an exocrine and an endocrine organ.
The digestive juices produced by the pancreas are secreted into the duodenum via a Y-shaped duct, at the point where the common bile duct from the liver and the pancreatic duct join just before entering the duodenum. In this way, a variety of digestive enzymes (trypsin, chymotrypsin, lipase, and amylase, among others) are delivered into the small intestine to aid in the digestion of proteins, fats, and carbohydrates. The enzymes are delivered in an inactive form called zymogens. The zymogens are activated by the chemical substances in the small intestine. The digestive enzymes carried into the duodenum are representative of the exocrine function of the pancreas, in which specific substances are made to be passed directly into another organ.
The pancreas is unusual among the body's glands in that it also has a very important endocrine function. Small groups of special cells called islet cells throughout the organ make such hormones as insulin and glucagon, which are critical in regulating blood sugar levels; and vasoactive intestinal peptide, which influences gastrointestinal activity. These hormones are secreted directly into the bloodstream to affect organs all over the body. No organ except the pancreas makes significant amounts of insulin or glucagon, but other tissues do produce vasoactive intestinal peptide. Insulin acts to lower blood sugar levels by allowing the sugar to flow into cells. Glucagon acts to raise blood sugar levels by causing glucose to be released into the circulation from its storage sites. Insulin and glucagon act in an opposite but balanced fashion to keep blood sugar levels stable.
Role in human health
A normal pancreas is important for maintaining good health, preventing malnutrition, and maintaining normal levels of blood sugar. The digestive tract needs the help of the enzymes produced by the pancreas to reduce food particles to their simplest elements, or the nutrients cannot be absorbed. Carbohydrates must be broken down into individual sugar molecules. Proteins must be reduced to simple amino acids. Fats must be broken down into fatty acids. The pancreatic enzymes are important in all these transformations. The basic particles can then easily be transported into the cells that line the intestine, and from there they can be further altered and transported to different tissues in the body as fuel sources and construction materials.
Similarly, the body cannot maintain normal blood sugar levels without the balanced action of insulin and glucagon. Both hypoglycemia (low blood sugar) and hyperglycemia (high blood sugar) cause symptoms and serious health problems.
Common diseases and disorders
Glucose is a simple sugar molecule, but one that is necessary to every type of cell as a major source of energy. Insulin made in the pancreas has a critical role in permitting glucose to enter cells. Without insulin, the cells of the body literally "starve in the midst of plenty," and are unable to make use of sugar in the blood even if blood sugar levels are very high. This condition is called diabetes mellitus. Diabetes actually represents a collection of disorders resulting in high blood sugars related to abnormal insulin levels, or abnormalities of the receptor that binds the insulin to allow glucose to enter the cell. Diabetes is quite common in the United States, affecting 1% of the general population.
Type I diabetes, which is sometimes called insulin-dependent diabetes, is a disease in which a patient must use insulin regularly to avoid serious problems with cells starving for glucose and acidic waste products accumulating in the blood. In this form of diabetes, the pancreas is essentially not producing insulin. Pancreas transplantation is a method of treating type I diabetes that has achieved success rates of 805% in the past decade, success being defined as the organ recipient's remaining insulin-independent. In type II diabetes, or non-insulin-dependent diabetes, blood sugar levels can often be controlled with diet, exercise, and medications taken by mouth. In some forms of type II diabetes the pancreas is not producing enough insulin; in other cases the receptor that binds insulin is no longer sensitive to it, or too few receptors are made by the cells that need glucose. Sometimes a combination of these problems is present. Gestational diabetes mellitus (GDM) is a third type of diabetes, which is a temporary problem with blood sugar levels that exists only during pregnancy. Women with GDM, however, need to know they are at increased risk for developing type II diabetes.
Pancreatitis is a relatively common condition that affects the pancreas. It can occur as an acute (sudden onset) problem or chronic (slow, ongoing) disorder. The common element in both types is inflammation caused by the normal digestive enzymes of the pancreas. In pancreatitis, these secretions act abnormally and start to digest the pancreas itself. Between 50,000 and 80,000 people in the United States develop acute pancreatitis every year, usually related to gallstones or alcohol abuse. Most patients recover within a week, but the most severe forms of pancreatitis have a mortality rate of 10%. Chronic pancreatitis is slow and insidious in onset, and
so harder to diagnose. Alcohol use is the most common cause of deterioration in pancreatic function over time. Without adequate levels of enzymes and hormones produced by the pancreas, such diseases as diabetes mellitus and malabsorption syndromes will develop. A malabsorption syndrome is a condition in which the body is not able to absorb the nutrients it needs from the food it attempts to digest. Vitamin deficiencies, protein malnutrition, and problems with frequent, greasy stools may occur.
Complications of pancreatitis include pancreatic necrosis (the death of a significant portion of the cells in the pancreas, putting the patient at risk of bleeding, infection, shock, and failure of many major organs); pancreatic abscess (an infection with a wall of scar tissue around it); and pancreatic pseudocyst (a pocket full of fluid and pancreatic enzymes that may shrink, expand, or rupture). Patients with chronic pancreatitis are also at increased risk of developing cancer of the pancreas.
Amino acidshe category of molecules used to build proteins.
Diabetes mellitus chronic form of diabetes in which insulin does not effectively transport glucose from the bloodstream.
Duodenumhe portion of the small intestine that lies between the stomach and the jejunum. The pancreas empties some of its secretions into the duodenum via a Y-shaped duct.
Endocrine type of gland that secretes hormones directly into the blood or lymph.
Enzymesomplex protein molecules that speed up chemical reactions, or make reactions happen under conditions where they normally would not occur.
Exocrine type of gland that secretes its products to an epithelial surface.
Glucagon hormone secreted by the pancreas that opposes insulin in the regulation of blood sugar levels.
Insulin hormone produced in the islet cells of the pancreas that regulates the metabolism of glucose and other nutrients.
Islet cellsndocrine cells in the pancreas that are specialized to secrete glucagon or insulin.
Jaundice condition in which the skin and whites of the eyes are yellow because of bile products retained in the bloodstream.
Pancreatitisnflammation of the pancreas.
Zymogensnzyme precursor molecules that may change into enzymes as a result of catalytic change.
Cancer of the pancreas
Pancreatic cancer is a major cause of death from cancer around the world. Tumors of the pancreas may arise from either endocrine or exocrine cells. Some rare types of pancreatic tumors hypersecrete either glucagon (glucagonomas) or insulin (insulinomas). Cancer of the pancreas is difficult to diagnose in its early stages; about 90% of patients present with pain, diarrhea, blood clots, weight loss, or jaundice when the cancer has already spread outside the pancreas. As of 2001, about 25,000 people die every year with this disease, and there are few medical interventions to help these patients. Under certain circumstances, chemotherapy or surgery to remove part of the pancreas may be attempted. Only 2% of patients are alive five years after being diagnosed.
"Gastrointestinal Disorders." Section 3 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.
Izenberg, Neil, et al. Human Disease and Conditions. New York: Charles Scribner's Sons, 2000.
Tierney, Laurence M., Stephen J. McPhee, and Maxine A. Papadakis. Current Medical Diagnosis and Treatment 2001. New York: McGraw-Hill, 2001.
American Diabetes Association. 1660 Duke Street, Alexandria, VA 22314. (800) 232-3472.
National Digestive Diseases Information Clearinghouse. 2 Information Way, Bethesda, MD 20892. (301) 654-3810 or (800) 891-5389.
National Institutes of Health. <<a href="http://www.niddk.nih.gov">http://www.niddk.nih.gov>.
Pancreas Foundation. <<a href="http://www.pancreasfoundation.org">http://www.pancreasfoundation.org>.
Erika J. Norris