Pancreatic Secretion Flashcards
What are the two components of pancreatic secretion?
1) Aqueous secretion
2) Enzymatic
Aqueous secretion comes from where?
Duct cells
Aqueous secretion consists of what?
Water and Bicarbonate
Note that the aqueous secretion of the pancreas, the water and bicarbonate, are secreted at about the same rate as the gastric secretion of the stomach. That is, this pancreatic secretion exists to neutralize gastric acid.
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The enzymatic portion of pancreatic secretion comes from where?
Acinar cells
Acinar cells make up what percentage of the pancreas
80
What the hell does the centroacinar cell do?
It regulates the water and electrolyte component of the aquous secretion. Secretin regulates it.
Smoking limits pancreatic secretions. May lead to duodenal ulcer because it limits bicard secretion
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In the absence of pancreatic secretion, we see?
maldigestion, especially of protein and fat
What is the major regulator of pancreatic enzyme secretion
CCK
Does the Pancreas contain CCK receptors
no. Then how does CCk regulate pancreatic enzyme secretions? Triggers vagal-vagal reflexes in which Ach is the neurotransmitter which stimulates the pancreas.
Know the mechanism of pancreatic secretion slide
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Water is broked down into OH and H, OH combines with CO2 to make bicarb and the bicarb goes out into the lumen while the H goes out into the blood.
Blood of the pancreas has a lower pH.
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Pancreatic secretion depends on what transporter
Na/K ATPase…the Na has to be pumped out because it is then brought back in to fuel the secondary active transport of hydrogen
What exactly does Secretin do?
Activates the CF channel, thus moving chloride into the lumen to fuel the transport of bicarb.
Enzymes are secreted on what cell structure
Rough ER
Enzymes are secreted in what way to prevent the degradation
With a leader of Hydrophobic Amino acids
Enzymes are membrane contained from the moment of their release from the RER…KNOW
this is an important mechanism that prevents teh enzymes from digesting the pancreatic tissue
Enzymes are budded off into what when they leave the RER?
Transitional elements
Transitional elements become—–
smooth golgi vesicles
Smooth gologi vesicles become—
Condensing vacuoles
RER—Transitional elements—smooth golgi vessicles— condensing vacuoles
summary so far
WHat occurs within the condensing vacuoles
Water is pumped out. Enzymes become proenzymes…these proenzymes are concentrated and stored as zymogen granules.
Zymogen granules do what?
They migrate to the luminal aspect of the cell and wait until the secretory stimulus arrives
The type of enzymes released depends on what?
Diet
More protein= More trypsin
More carbs= More amylase
Threshold pH for secretin release?
4.5
Maximal secretin release
pH 3
What stimulates S cells to produce secretin during the intestinal phase?
Hydrogen ion, fat, protein entering the duodenum stimulates S cells to make secretin which tehn stimulates duct cells to make water and bicarb in order to neutralize the environment for pancreatic enzymes.
What stimulates I cells to produce cck
Fatty acids and amino acids stimulate CCK release from the I cells. This CCK relelase leads to a vagal vagal reflex where Ach is the effector. Initiates the release of enzymes from Acinar cells and also potentiates the effect of secretin on duct cells….leads to maximum HCO3 release.
KNOW THAT SECRETIN is POTENTIATED BY CCK
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