PANCREAS
The pancreas
is a glandular organ in the digestive system and endocrine system of vertebrates. In humans, it is
located in the abdominal cavity
behind the stomach. It is an endocrine gland producing several
important hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide
which circulate in the blood. The pancreas is also a digestive organ, secreting
pancreatic juice
containing digestive
enzymes that assist digestion and
absorption of nutrients in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.
The
pancreas is an endocrine
organ that lies in the abdomen,
specifically the upper left
abdomen. It is found behind the stomach, with
the head of the pancreas surrounded by the duodenum. The pancreas is about 15 cm
(6 in) long.
Anatomically,
the pancreas is divided into a head, which rests within the concavity of
the duodenum, a body lying behind the base of the stomach, and a tail, which ends abutting
the spleen. The neck of the pancreas lies
between the body and head, and lies anterior to the superior mesenteric
artery and vein. The
head of the pancreas surrounds these two vessels, and a small uncinate
process emerges from the lower part of the head, lying behind the superior
mesenteric artery.
The pancreas is a secretory
structure with a internal hormonal role
(endocrine) and an external digestive role
(exocrine). It has two main ducts, the main pancreatic duct,
and the accessory pancreatic
duct. These drain enzymes through the ampulla of Vater into the duodenum.
Function:-
The pancreas is a dual-function
gland, having features of both endocrine and exocrine glands.
Endocrine
The part of the pancreas with
endocrine function is made up of approximately a million[8] cell clusters called islets of Langerhans.
Four main cell types exist in the islets. They are relatively difficult to
distinguish using standard staining techniques, but they can be classified by
their secretion: α alpha cells
secrete glucagon (increase glucose in blood), β beta cells secrete insulin (decrease glucose in blood), Δ delta cells secrete somatostatin (regulates/stops α and β cells) and PP cells, or γ (gamma) cells, secrete pancreatic polypeptide.[9]
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,
either by cytoplasmic processes or by direct apposition.
Exocrine
The pancreas also functions as
an exocrine gland that assists the digestive system. It secretes pancreatic fluid
that contains digestive enzymes that pass to the small intestine. These enzymes
help to further break down the carbohydrates, proteins and lipids (fats) in the
chyme.
In humans, the secretory
activity of the pancreas is regulated directly via the effect of hormones in the blood on the islets of Langerhans
and indirectly through the effect of the autonomic nervous system
on the blood flow.[11]
The exocrine component of the
pancreas, often called simply the exocrine pancreas, is the portion
of the pancreas that performs exocrine functions. It has ducts that 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 is 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.
|
Secretion
|
Cell
producing it
|
Primary
signal
|
|
bicarbonate ions
|
||
|
Basophilic
cells
|
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 primarily
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. Secreted to a lesser degree are pancreatic lipase and pancreatic amylase. The pancreas also secretes phospholipase A2, lysophospholipase, and cholesterol esterase.
Clinical relevance
A puncture of the pancreas,
which may lead to the secretion of digestive enzymes such as lipase and amylase
into the abdominal cavity as well as subsequent pancreatic self-digestion and
digestion and damage to organs within the abdomen, generally requires prompt
and experienced medical intervention.
It is possible for one to live
without a pancreas, provided that the person takes insulin for proper regulation
of blood glucose concentration and pancreatic enzyme supplements to aid
digestion.
Inflammation of the pancreas is
known as pancreatitis. Pancreatitis is most often associated with recurrent gallstones or chronic alcohol use, although a
variety of other causes, including measles, mumps,
some medications, the congenital condition alpha-1
antitrypsin deficiency and even some scorpion stings, may cause
pancreatitis. Pancreatitis is likely to cause intense pain in the central abdomen, that often radiates to the back, and may
be associated with jaundice. In
addition, due to causing problems with fat digestion and bilirubin excretion, pancreatitis often presents
with pale stools and
dark urine.[14]
In pancreatitis, enzymes of the
exocrine pancreas damage the structure and tissue of the pancreas. Detection of
some of these enzymes, such as amylase and lipase in the blood, along with symptoms and
findings on X-ray, are often used to indicate that a person
has pancreatitis. A person with pancreatitis is also at risk of shock.
Pancreatitis is often managed medically with analgesics, removal of gallstones or treatment of
other causes, and monitoring to ensure a patient does not develop shock.[14]
Pancreatic cancers, particularly
the most common type, pancreatic adenocarcinoma, remain very difficult to treat,
and are mostly diagnosed only at a stage that is too late for surgery, which is
the only curative treatment. Pancreatic cancer is rare in those younger than
40, and the median age of diagnosis is 71.[15] Risk factors include: smoking, obesity, diabetes, and certain rare genetic conditions
including: multiple
endocrine neoplasia type 1 and hereditary
nonpolyposis colon cancer among others. About 25% of cases are
attributable to tobacco smoking,
while 5-10% of cases are linked to inherited genes.
There are several types of
pancreatic cancer, involving both the endocrine and exocrine tissue. Pancreatic
adenocarcinoma, which affects the exocrine part of the pancreas, is by far the
most common form. The many types of pancreatic endocrine
tumors are all uncommon or rare, and have varied outlooks. However
the incidence of
these cancers has been rising sharply; it is not clear to what extent this
reflects increased detection, especially through medical imaging, of tumors that would be very slow
to develop. Insulinomas
(largely benign) and gastrinomas
are the most common types.[18] In the United States pancreatic cancer
is the fourth most common cause of deaths due to cancer.[19] The disease occurs more often in the
developed world, which had 68% of new cases in 2012.[20] Pancreatic adenocarcinoma typically has
poor outcomes with the average percentage alive for at least one and five years
after diagnosis being 25% and 5% respectively.[20][21] In localized disease where the cancer
is small (< 2 cm) the number alive at five years is approximately 20%.[22] For those with neuroendocrine cancers
the number alive after five years is much better at 65%, varying considerably
with type.[20]
Preventing Pancreatitis
There are ways you can protect
your pancreas and reduce your risk for pancreatitis and other serious health
problems like EPI:
1. Limit alcohol
consumption. By drinking less or not at all, you can help protect your
pancreas from the toxic effects of alcohol and reduce your risk for
pancreatitis. A number of studies, including a population-based study in
Denmark involving 17,905 people, found that high alcohol intake is associated
with an increased risk of pancreatitis in both men and women.
2. Eat a low-fat diet.
Gallstones, a leading cause of acute pancreatitis, can develop when too much
cholesterol accumulates in your bile, the substance made by your liver to help
digest fats. To reduce your risk for gallstones, eat a low-fat diet that includes whole grains and
a variety of fresh fruits and vegetables. To help prevent pancreatitis,
specific foods to avoid include fatty or fried foods as well as full-fat dairy
products. High triglyceride levels, or the amount of fats carried in your
blood, can increase your risk for acute pancreatitis. So, it's also important
to limit foods high in simple sugars, such as sugary sweets and high-calorie
beverages, that could raise your triglyceride levels.
3. Exercise regularly
and lose excess weight. People who are overweight are more likely to
develop gallstones, putting them at greater risk for acute pancreatitis. Losing
extra pounds gradually and maintaining a healthy weight by eating a balanced
diet and engaging in regular physical activity can help prevent gallstones from
forming.
4. Skip crash diets.
The caveat to losing weight is to do it gradually. When you go into crash-diet
mode, prompting quick weight loss, your liver ramps up cholesterol production
in response, which increases your risk for gallstones.
5. Don't smoke.
Studies show that smoking cigarettes is linked to acute pancreatitis.
Researchers in Sweden followed 84,667 healthy women and men between the ages of
46 and 84 to examine how smoking affected their risk for acute pancreatitis.
The study, published in the journal Gut, revealed that people who
smoked the equivalent of at least one pack of cigarettes a day for 20 years had
more than double the risk for non-gallstone-related acute pancreatitis than
non-smokers had. Quitting smoking reduced the smokers' risk for acute
pancreatitis to the same level as that of non-smokers.
