The Exocrine Pancreas Flashcards
what are the two types of glandular tissue within the pancreas?
exocrine and endocrine
are the islets within parenchyma of glands endo or exocrine?
endocrine
exocrine glands are ___ enzymes
digestive
what is pancreatic juice rich in?
digestive enzymes and bicarb
pancreatic fluids drain into…
SI (duodenum) via separate bile and pancreatic ducts
which species have pancreatic fluids drain through a COMMON DUCT?
goat, sheep, humans
what does obstruction/inflammation of pancreatic ducts cause?
pancreatitis
what happens when food enters the duodenum?
neutralizes stomach acids
pH changes very quickly
the ion transport of pancreatic duct cells is ___ but directionally ___ to that of parietal cells
similar but opposite
what enzymes for digestion does pancreatic juice provide?
amylase
lipase
protease
what does amylase do?
breaks down glc polymers
what does lipase do?
digest triglycerides, phospholipids, and cholesterols
what do proteases do?
breaks down proteins to aa, di/tri/oligo-peptides
what do pancreatic acinar cells secrete?
enzymatic components (pro-enzymes)
what is meant by ecbolic secretion?
protein secretion by acinar cells
proenzymes are stored in…
zymogen granules
zymogen granules are released via…
exocytosis
bicarb is ___ secreted by pancreas
actively
what do centroacinar and ductal cells secrete?
aqueous fraction aka electrolytes, bicarb, water
what is hydroelastic secretion from the pancreas?
alkaline and watery secretion by duct cells
what do ductal cells to to pancreatic fluid?
modify it, remove Cl- and add bicarb to make it alkaline
pancreatic bicarb secretion into duodenum is essential for…
gastric acid neutralization
bicarb is secreted via what exchanger?
Cl/bicarb exchange, which is driven by bicarb gradient
which proteins maintain the bicarb gradients?
- Na/bicarb transport
- intracell carboanhydrase (CA)
- Na/K ATPase
- proton pump
- Na/H exchange
- Cl channel
- water follows via osmotic gradient
composition of pancreatic juice depends on…
rate of secretion aka flow rate
at LOW pancreas flow rates, ___ is main anion
Cl-
at HIGH pancreas flow rates, ___ concentration increases
bicarb
which hormone stimulates secretory/flow rate?
secretin
bicarb concentration ___ at higher flow rates
increases
what does CCK and gastrin stimulate in the pancreas?
stimulates acinar cells to secrete proenzymes
what does secretin stimulate in pancreas?
duct cells to secrete water and bicarb
what does vagal input do to the pancreas?
stimulates BOTH acinar and duct cells
___ hormonal and ___ neural control mechanism stimulates pancreatic secretion
2 hormonal
1 neural
what are the three mechanisms that stimulate pancreatic secretion?
- vagal input stim acinar and duct cells
- CCK and gastrin stim acinar cells
- secretin stim duct cells
what are the three phases of pancreatic secretion?
- cephalic phase
- gastric phase
- intestinal phase
what is the cephalic phase of pancreatic secretion?
sight, smell, taste, anticipation
what is the gastric phase of pancreatic secretion?
stomach distension
what is the intestinal phase of pancreatic secretion?
arrival of food into the SI
which phase of pancreatic secretion includes acinar and duct cell response?
intestinal
which is the most important phase of pancreatic secretion? why?
intestinal phase!
controls 80% of secretion
when during the intestinal phase is CCK released and why?
in response to fats and aa’s in duodenum
released from I cells, enters circulation and stim acinar cells
when during the intestinal phase is gastrin released and why?
in response to peptides and aa’s in stomach
released from G cells, stim acinar cells
which 3 hormones stimulate enzyme secretion?
ACh, CCK, gastrin
when during the intestinal phase is secretin released and why?
in response to low pH in duodenum
released from S cells to stim duct secretion (bicarb)
what hormones are part of the enteropancreatic reflex?
CCK - due fats and aa in duodenum
gastrin - due to peptides and aa in stomach
secretin - low SI pH
what are the two players of endocrine control of pancreatic juice secretion?
CCK and secretin
where is CCK synthesized and released from?
peptide hormone
enteroendocrine I cells
where can you find I cells?
duodenum, jejunum, ileum
what’s the stimulator for I cells?
fatty acids and aa
what is the target of CCK?
acinar cells
which organs does CCK act on?
gallbladder, pancreas, stomach, sphincter of bile aka pancreatic duct
where is secretin synthesized and released from?
peptide hormone released by enteroendocrine S cells
where can you find S cells?
duodenum
what is a stimulator of secretin S cells?
low pH (<4.5) in duodenum
what does secretin target?
duct cells
increasing levels of secretin ___ secretory flow rate
increases
increasing levels of secretin increase flow rate, which causes ___ in fluid composition
change
enzymes are activated and work best in an ___ environment
alkaline
where are digestive enzymes activated?
duodenum
why is digestive enzyme activation such a complex mechanism?
protective mechanism against autodigestion
explain the process of digestive enzyme activation in the duodenum
- inactive proenzymes (zymogens) are synthesized
- proenzymes are stored in vesicles
- proenzymes are activated in intestinal lumen
- trypsinogen is cleaved by ENTEROKINASE
- trypsin activates other proenzymes
where is anti-trypsin factor produced?
acinar cells
trypsin activates…
other proenzymes
?
pancreatitis!
what is pancreatitis?
inflammation of pancreas with histological presence of edema, neutrophilic infiltrate, necrosis
pancreatitis occurs when digestive enzymes are activated upon release into ___ system, causing ____ and ___
pancreatic duct system
causes autophagy and inflammation
issues with normal pancreatic juice secretion ___ zymogen granules, and proenzymes become ___ in ducts. this causes ___ activation
increases granules
proenzymes get trapped
PREMATURE activation
spontaneous cleavage of ___ causes premature activation of all zymogens
trypsinogen
what are symptoms of pancreatitis?
anorexia, lethargy, exercise intolerance, V, D, abdomen pain, dehydration, fever, arrhythmia
in patients with pancreatitis, total serum lipase is ___
increased
what are pancreatic lipases typically produced by>
pancreatic acinar cells
what’s the etiology of pancreatitis?
idiopathic
what’s the key factor initiating pancreatic inflammation?
activation of trypsin within acinar cells
