Abnormal Digestion of Food in the
Small Intestine-Pancreatic Failure
A serious cause of abnormal digestion is failure of the pancreas to
secrete pancreatic juice into the small intestine. Lack of pancreatic
secretion frequently occurs (1) in pancreatitis
(which is discussed later), (2) when the pancreatic
duct is blocked by a gallstone at the papillaof Vater, or (3) after the head of the pancreas has beenremoved because
of malignancy.
Loss of pancreatic juice means loss of trypsin, chy-motrypsin,
carboxypolypeptidase, pancreatic amylase, pancreatic lipase, and still a few
other digestive enzymes. Without these enzymes, as much as 60 per cent of the
fat entering the small intestine may be unab-sorbed, as well as one third to
one half of the proteins and carbohydrates. As a result, large portions of the
ingested food cannot be used for nutrition, and copious, fatty feces are
excreted.
Pancreatitis. Pancreatitis means
inflammation of thepancreas, and this can occur in the form of either acutepancreatitis or chronic pancreatitis.
The most common cause of pancreatitis is drinkingexcess alcohol, and the second most common cause is blockage of the papilla of Vater by a
gallstone; the twotogether account for more than 90 per cent of all cases. When
a gallstone blocks the papilla of Vater, this blocks the main secretory duct
from the pancreas as well as the common bile duct. The pancreatic enzymes are
then dammed up in the ducts and acini of the pancreas. Even-tually, so much
trypsinogen accumulates that it over-comes
the trypsin inhibitor in the secretions, and a smallquantity of trypsinogen
becomes activated to form trypsin. Once this happens, the trypsin activates
still more trypsinogen as well as chymotrypsinogen and car-boxypolypeptidase,
resulting in a vicious circle until most of the proteolytic enzymes in the
pancreatic ducts and acini become activated. These enzymes rapidly digest large
portions of the pancreas itself, sometimes completely and permanently
destroying the ability of the pancreas to secrete digestive enzymes.
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