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8 out of 11

The mechanism that protects normal pancreas from autodigestion is:

A Secretion of bicarbonate

B Protease inhibitors present in plasma

C Proteolytic enzymes secreted in inactive form

D The resistance of pancreatic cells

Ans. C Proteolytic enzymes secreted in inactive form
  1. The pancreas has 3 important functions in digestion:

a. Secretion of sodium bicarbonate to neutralize hydrochloric acid from the stomach;

b. Secretion of digestive enzymes; and

c. Secretion of hormones to regulate intermediate metabolism after a meal.

  1. Except for amylase and lipase, all pancreatic enzymes are synthesized and secreted in an inactive form to protect the pancreas from autodigestion Q.
  2. All inactive enzymes are then activated by trypsin within the intestinal lumen.
  3. Trypsin itself is generated from trypsinogen by the action of enterokinase and previously activated trypsin .
  4. Activated trypsin can then activate other trypsinogen molecules and other proenzymes.
  5. Obviously, premature activation of trypsin within the pancreas would initiate the activation cascade and lead to pancreatic autodigestion.
  6. Fortunately, several protective mechanisms are in place to prevent premature activation of trypsinogen and the other proenzymes.
  7. Pancreatic secretory trypsin inhibitor (PSTI), or serine protease inhibitor, Kazal type 1 (SPINK1) is a trypsin inhibitor with a capacity of neutralizing approximately 20% of pancreatic trypsin activity.
  8. Prematurely activated trypsin is normally inhibited within the pancreas by PSTI/SPINK1 before it can activate other enzymes and cause pancreatitis.
  9. Other important protective mechanisms are low intracellular calcium concentrations, isolation of digestive enzymes into zymogen granules, and disposal of pancreatic enzymes into the intestinal lumen by the high flow rate of bicarbonate rich fluids in the ductal system. In addition, trypsin is also capable of feedback inhibition because trypsin can digest itself

GIT Flashcard List

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