1. Chapter 18
The Exocrine Pancreas

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Pancreas
 Exocrine:
 Acini:

Secrete
pancreatic
juice.
 Endocrine:
 Islets of
Langerhans:

Secrete
insulin and
glucagon.
Insert fig. 18.26

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 Contains H20, HC03
-
and digestive enzymes.
Pancreatic Juice

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 Pancreatic juice is alkaline with high
HCO3 content about 113 meq/L
 cations: Na, K, Ca, Mg (PH=8.0)
 Anions: HCO3,Cl,SO4,HPO4
 Digestive enzymes (95% of protein in
juice)

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 1500 ml of pancreatic juice /day
 Pancreatic juice together with bile and
intestinal juice neutralize gastric acid
raising duodenal PH to (6.0-7.0)

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ELECTROLYTES
 Produced by centroacinar and duct
cells
 Mainly in form of NaHCO3
 Conc. Of Na and K similar to blood
 Conc. Of HCO3 and Cl change
according to rate of flow of secretion
 Duct cells reabsorb HCO3 in exchange
for Cl.

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 Pancreas contain carbonic anhydrase
enzyme for formation of HCO3
 Acetazolamide (diomox) is a strong
inhibitor of carbonic anhydrase and
used for inhibition of pancreatic HCO3
secretion

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Pancreatic Juice
 Complete digestion of
food requires action of
both pancreatic and
brush border enzymes.
 Most pancreatic
enzymes are produced
as zymogens.
 Trypsin (when activated
by enterokinase)
triggers the activation of
other pancreatic
enzymes.
 Pancreatic trypsin
inhibitor attaches to
trypsin.
 Inhibits its activity in the
pancreas.
Fig. 18.29

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REGULATION OF
PANCREATIC SECRETION
 Mainly under hormonal control
 Secretin: acts on duct cells and
centroacinar cells to cause
secretion of alkaline juice rich in
HCO3 and poor in enzymes

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 CCK: acts on acinar cells to cause
release of zymogen granules (enzymes)
 Parasym. : Vagi cause secretion of
small amounts of pancreatic juice rich in
enzymes
 There is vagally mediated conditioned
reflex secretion of pancreatic juice in
response to sight or smell of food.