Encyclopedia of Health and Medicine

P
pancreas An elongated gland with both
endocrine and exocrine functions that lies beneath
the STOMACH on the upper left side of the
abdomen, beneath the lower ribs. Both realms of
function play roles in digestion, though the
endocrine functions of the pancreas are also significant
for maintaining the body’s GLUCOSE-INSULIN
balance and for regulating cellular use of glucose.
The main body of the pancreas is a loose collection
of secretory cells, looking somewhat like a
mass of fish eggs, that produce DIGESTIVE ENZYMES
and juices. These cells organize in lobular formations,
called acini, around ducts that channel their
secretions to the main pancreatic duct coursing
through the center of the pancreas (hence their
designation as exocrine). The pancreatic duct joins
the common BILE duct from the GALLBLADDER just
before the DUODENUM (the first segment of the
SMALL INTESTINE), adding its juices to the bile that
then flows into the duodenum.
Interspersed among the secretory cells are about
a million clusters of specialized cells that produce
the hormones INSULIN, GLUCAGON, and SOMATOSTATIN.
Called the ISLETS OF LANGERHANS, these clusters are
the endocrine glands of the pancreas. An extensive
BLOOD supply infiltrates the islets, which secrete
their hormones directly into the bloodstream
(hence their designation as endocrine). These hormones
regulate numerous functions of METABOLISM
throughout the body, including many that take
place in the gastrointestinal system.
Pancreatic Enzymes and Juices
The pancreas produces numerous enzymes essential
for digestion. DIGESTIVE HORMONES trigger their
release. Key among the digestive enzymes are
• proteases, notably trypsin and chymotrypsin,
which break down proteins; to protect itself
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from these proteases hydrolyzing its own tissue,
the pancreas secretes them in proenzyme
forms, trypsinogen and chymotrypsinogen, that
an enzyme in the duodenum, enterokinase,
activates
• pancreatic lipase, which breaks down dietary
triglyceride into fatty acid molecules the intestinal
mucosa can absorb
• amylase, which breaks down dietary starches
(plant-based stored carbohydrates) into disaccharides
(multiple molecule sugars) in preparation
for further digestion later in the small
intestine
• ribonuclease and deoxyribonuclease, which
break down nucleic acids (chemicals that facilitate
the body’s use of proteins)
• elastase, which facilitates the break down of
proteins into amino acids
• bicarbonate, which neutralizes gastric acid in the
chyme (mixture of food and gastric juices) that
flows from the stomach into the duodenum
Pancreatic Hormones
The primary hormones the pancreas produces are
insulin, glucagon, and somatostatin. Insulin is key
to carbohydrate and lipid (fatty acid) metabolism,
in the gastrointestinal tract as well as at the cellular
level throughout the body. The pancreas
releases insulin in response to digestive hormones
the gastrointestinal tract secretes as food enters
the various stages of digestion. Insulin regulates
glucose levels in the blood by controlling how
much, and when, glucose enters the cells. It also
signals the LIVER to convert excess glucose to the
storage form glycogen. Somatostatin slows the
release of insulin. Glandular tissue in the intestinal
mucosa also produces somatostatin, which