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The pancreas is very important organ in the digestion system and the circulatory system because it helps to maintain
our blood sugar levels. The pancreas is considered to be part of the gastrointestinal system. It 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.
It has a pear-shape to it and is approximately 6 inches long. It is located in the middle and back portion of the
abdomen. The pancreas 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: any substance secreted by the cells of the pancreas will be
secreted outside of the 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. 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.
Note: The pancreas is both an exocrine and an endocrine 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 the hormones of insulin and glucagon. These, of
course, are hormones that are critical in regulating blood sugar levels. 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.
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.
A healthy working pancreas in the human body is important for maintaining good health by 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.
The pancreas contains exocrine and endocrine cells. Groups of endocrine cells, the islets of Langerhans, secrete two
hormones. The beta cells secrete insulin; the alpha cells secrete glucagon. The level of sugar in the blood depends
on the opposing action of these two hormones.
Insulin decreases the concentration of glucose in the blood. Most of the glucose enters the cells of the liver and
skeletal muscles. In these cells, this monosaccharide is converted to the polysaccharide glycogen. Therefore, insulin
promotes glycogenesis (glycogen formation), stimulating the breakdown of glycogen into glucose for release into the
blood.
Insulin deficiency leads to the development of diabetes mellitus, specifically type I, juvenile diabetes. As the
pancreas does not produce sufficient insulin, it is treated by insulin injections. In type II or maturity onset diabetes,
the pancreas does produce enough insulin, but the target cells do not respond to it.
As already stated, the pancreas is a mixed gland having both endocrine and exocrine functions. The exocrine portion
secretes digestive enzymes into the duodenum via the pancreatic duct. The endocrine portion secretes two hormones,
insulin and glucagon, into the blood.
Insulin is a hormone that acts directly or indirectly on most tissues of the body, with the exception of the brain. The
most important action of insulin is the stimulation of the uptake of glucose by many tissues, particularly the liver,
muscle and fat. The uptake of glucose by the cells decreases blood glucose and increases the availability of glucose
for the cellular reactions in which glucose participates. Thus, glucose oxidation, fat synthesis, and glycogen synthesis
are all accentuated by an uptake of glucose. It is important to note that insulin does not alter glucose uptake by the
brain, nor does it influence the active transport of glucose across the renal tubules and gastrointestinal epithelium.
As stated, insulin stimulates glycogen synthesis. In addition, it also increases the activity of the enzyme that
catalyzes the rate-limiting step in glycogen synthesis. Insulin also increases triglyceride levels by inhibiting
triglyceride breakdown, and by stimulating production of triglyceride through fatty acid and glycerophosphate
synthesis. The net protein synthesis is also increased by insulin, which stimulates the active membrane transport of
amino acids, particularly into muscle cells. Insulin also has effects on other liver enzymes, but the precise
mechanisms by which insulin induces these changes are not well understood.
Insulin is secreted by beta cells, which are located in the part of the pancreas known as the islets of Langerhans.
These groups of cells, which are located randomly throughout the pancreas, also consist of other secretory cells
called alpha cells. It is these alpha cells that secrete glucagon. Glucagon is a hormone that has the following major
effects: it increases hepatic synthesis of glucose from pyruvate, lactate, glycerol, and amino acids (a process called
gluconeogenesis, which also raises the plasma glucose level); and it increases the breakdown of adipose tissue
triglyceride, thereby raising the plasma levels of fatty acids and glycerol. The glucagon secreting alpha cells in the
pancreas, like the beta cells, respond to changes in the concentration of glucose in the blood flowing through the
pancreas; no other nerves or hormones are involved.
It should be noted that glucagon has the opposite effects of insulin. Glucagon elevates the plasma glucose, whereas
insulin stimulates its uptake and thereby reduces plasma glucose levels; glucagon elevates fatty acid concentrations,
whereas insulin converts fatty acids and glycerol into triglycerides, thereby inhibiting triglyceride breakdown.
The alpha and beta cells of the pancreas make up a push-pull system for regulating the plasma glucose level.
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