Physiology 3120 Lecture Notes - Lecture 14: Bilirubin, Mononuclear Phagocyte System, Micelle

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Woods Lecture 14
-pancreas is accessory organ that produces a lot of enzymes for nutrient digestion
-without exocrine pancreas, severe malnutrition and death by starvation due to insufficient
nutrient absorption! even though all those other organs still function
-acinar cells form circular structure around central duct  primary secretion
-make enzymes that get secreted into small duct that join bigger ducts until reach pancreas
-duct cells lining ducts modify acinar secretions  secondary secretion
-modifications are adding more/less bicarb or adding more/less water
 Pancreatic secretions can be more alkaline/more watery OR less alkaline/less watery
depending on what is being eaten
1. Bicarbonate – secreted by duct cells to neutralize acidic chyme that enters duodenum
2. Pancreatic Amylase – secreted by acinar cells, identical to salivary amylase that breaks down
starch, active in neutral envt of duodenum
3. Trypsinogen  Trypsin – zymogen where inactive trypsinogen secreted by acinar cells must be
cleaved into active trypsin to break down protein (more in next slide)
4. Chymotrypsinogen  Chymotrypsin – zymogen where inactive chymotrypsinogen secreted by
acinar cells must be cleaved into active chymotrypsin to break down protein
5. Procarboxypeptidase  Carboxypeptidase – zymogen where inactive procarboxypeptidase
secreted by acinar cells must be cleaved into active carboxypeptidase to break down protein
6. Proelastase  Elastase – zymogen where inactive proelastase secreted by acinar cells must be
cleaved into active elastase to break down protein
7. Pancreatic Lipase – secreted by acinar cells, breaks down lipids, active in neutral envt of
duodenum (different from lingual/gastric lipase)
8. Ribonuclease – secreted by acinar cells, breaks down RNAs present in animal products
9. Deoxyribonuclease - secreted by acinar cells, breaks down DNAs present in animal and plant
 Pancreas change type of enzymes secreted based on diet
-zymogens go through pancreatic duct to enter duodenum
-trypsinogen gets cleaved into trypsin by enterokinase which is brush border enzyme found
only in small intestine
-trypsin then acts as enzyme that cleaves all other zymogens ie: chymotrypsinogen,
procarboxypeptidase, proelastase (not shown)
-important that zymogens are not prematurely cleaved while still in pancreas as that would
damage pancreas
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