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36 Cards in this Set

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  • Back
Is fluid hyperosmotic or hyposmotic when it leaves the stomach?
hyperosmotic
What area is considered to be the endocrine portion of the pancreas and what do they secrete?
islets of langerhans - secrete insulin, somatostatin, glucagon, and pancreatic polypeptide; these are all secreted into blood
What is secreted from the exocrine pancreas?
enzyme, water, HCO3- secretion into pancreatic and common bile duct and thru sphincter of oddi
What is the purpose of having both acinar and duct cells providing secretion in the pancreas?
acinar cells - secrete enzymes
ductile cells - secrete water and electrolytes
** having 2 different secretion systems allows better adjustment of enzyme/liquid components
What is the significance of osmolarity dropping rapidly in the duodenum?
1) maintains fluid balance
2) provide digestive enzymes with ideal conditions
3) protection of mucosa
What is the difference between proximal and distal duct cells in the pancreas?
proximal duct cells - secrete water and bicarbinate
distal duct cells - reabsorbs water and bicarbonate
What is the effect of increased flow rate on pancreatic secretions?
1) high rates - net secretion is high in bicarbonate and low in chloride - reflective of primary secretion
2) vice versa at low rates - secondary secretion
*virually no change in cations wih change in flow rate
What is stored in a zymogen granule?
inactive proteolytic enzymes (proenzyme), and a trypsin inhibior (to avoid autodigestion of the pancreas)
What are the different types of enzymes found in the exocrine pancreas?
1) lipolytic (dig lipids)
2) amylases (dig CHO)
3) proteolytic (dig proteins)
What does pancreatic lipase do?
1) splits TGs into glycerol and FFAs (2FAs and a 2-monoglyceride)
2) requires oil/water interface, bile salts, and colipase
What linkage does pancreatic amylase cleave?
alpha 1,4 linkage of starch (creates maltose, maltotriose etc.)
Trypsin, chymotrypsin, and carboxypeptidase A and B are considered to be what general type of pancreatic enzyme?
proteolytic (digests proteins)
Describe the action of trypsin.
Endopeptidase active at basic amino acids.
Describe the action of chymotrypsin.
Endopeptidase active at aromatic amino acids.
Describe the action of carboxypeptidase A & B.
Exopeptidases active at C-term end; A active at aromatic and neutral amino acids and B active at basic amino acids
When pancreatic cells release granules, do all have the same % of enzymes?
YES!
What type of pancreatic enzymes make up 75% of the pancreatic enzymes?
Proteolytic (proteases including endopeptidases, and exopeptidases)
Which is a more important method of pancreatic secretion control, neural or hormonal?
Hormonal (secretin, CCK, and PP)
What pH triggers the release of secretin from the mucosal cells?
pH<4 in the duodenal lumen
Which hormones/neural peptides bind to Acinar cells? via their receptors that are located there?
1) VIP
2) GRP
3) CCK
4) ACh
Which hormones/neural peptides bind to duct cell in the pancreas via their receptors that are located there?
1) secretin
2) ACh
What cells does secretin stimulate to secrete bicarbonate and water?
1) pancreatic duct cells
2) duodenal glands
3) hepatocytes
What receptors does CCK act on in the pancreas?
CCK-A receptors
What type of response does most of CCKs activity come from?
long arc vago-vagal reflex
When is PP secreted and what does it do?
pancreatic polypeptide (PP) is an inhibitory regulator (inhibits vagal output from CNS)that is secreted during the meal and turns off the excitatory inputs on acinar cells
*proximal feedback loop
What is PYY and when is it secreted?
PYY is secreted from the ileum after a meal and inhibis gastric acid secretion, pancreatic enzyme secretion, and decreases transport
*distal feedback loop
What are the 3 phases of postprandial pancreatic secretion?
1) cephalic (25% of response)
2) gastric (10%)
3) intestinal (50-75%)
Which pancreatic secretion phases are neurally regulated and which are hormonally regulated?
1) neural - cephalic and gastric
2) hormonal - intestinal
Explain stimulus secretion coupling of pancreatic acinar cell secretion.
Receptors for two different things (ex. VIP and secretin) couple throuh the same pathway (ex. G protien) and potentiate each other.
How much fluid is secreted by enterocytes/day?
1000ml/day
(about 3000 ml total is secreted into the intestine, but much of that is from non-enterycte origin)
Where is the oldest enterocyte located on a villus structure?
at the tip of the villus where it will be sloughed off
Explain how the enterocyte changes its function as it moves up the villus.
crypt - net secretory cell
tip - net absorptive cell
What ion is coupled with the secretion of water in an enterocyte?
Cl-

(via the cystic fibrosis transmembrane regulator (CFTR) on the apical membrane)
How does cholera toxin work?
irreversibly activates G protein coupled to adenylate cyclase, increasing cAMP and keeping CFTR channel open (lose Cl-, Na+, and water)
What makes up most of the colonic secretion?
mucus
What does interdigestive secretion do?
gastric, bilary, and pancreatic fluid and enzymes is released periodically between meals to clear and clean the gut