The Exocrine Functions Of The Pancreas

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 H
2
0, HC0
3
-
and digestive enzymes.
Pancreatic Juice

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Pancreatic juice is alkaline with high
HCO
3
content about 113 meq/L
cations: Na, K, Ca, Mg (PH=8.0)
Anions: HCO
3
,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 NaHCO
3
Conc. Of Na and K similar to blood
Conc. Of HCO
3
and Cl change
according to rate of flow of secretion
Duct cells reabsorb HCO
3
in exchange
for Cl.

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Pancreas contain carbonic anhydrase
enzyme for formation of HCO
3
Acetazolamide (diomox) is a strong
inhibitor of carbonic anhydrase and
used for inhibition of pancreatic HCO
3

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
HCO
3
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.