Secretions of GI Tract and Pancreas Flashcards
What are the 3 main functions that saliva serves?
- initial digestion of starches and lipids
- dilution and buffering of ingested foods
- lubrication of ingested foods with mucus
Which of the following cells have motile extensions that contract when stimulated to eject saliva into the mouth?
A. Acinar cells
B. Myoepithelial cells
C. Ductal cells
D. All of the above
Myoepithelial cells
Which of the follwoing is the relative tonicity of saliva in comparison to plasma?
A. Hypertonic; with lower K+ and higher Na
B. Isotonic; with higher K+ and lower Na
C. Hypotonic; with higher K+ and lower Na
D. Hypotonic; with lower K+ and higher Na
C. Hypotonic; with higher K+ and lower Na
Which of the followign portions of the salivary gland is lined with columnar epithelial cells called ductal cells that act to modify initial saliva to hypotonic fluid?
A. Acinus
B. Intercalated duct
C. Striated duct
Striated duct
Transporters exist on the membrane of salivary ductal cells to form a net secretion of HCO3 and K+, and a net absorption of Na and Cl. What 3 exchangers are found on the luminal membrane of the Ductal cells in the salivary gland to help create this net result?
Na/H exchanger
Cl/HCO3 exchanger
H/K exchanger
HCO3 leaves the salivary ductal cell via what two transport mechanisms?
Cl/HCO3 exchanger
CFTR Cl channel
T/F: In salivary glands there is net absorption of solute in that more NaCl is absorbed than KHCO3 is secreted
True
The following are all secreted by salivary acinar cells. Which of the following causes the initial digestion of carbohydrates, but is pH sensitive?
A. a-amylase
B. lingual lipase
C. mucin
D. IgA
E. Killakrin
a-amylase
Flow of saliva is modulated by both parasympathetics and sympathetic innervation, and both stimulate salivary secretion.
Parasympathetic input to salivary glands are carried on what two cranial nerves?
Ach is released on what receptors found on acinar and ductal cells?
What is the secondary messenger and the result of that messenger?
Facial N. and Glossopharyngeal N.
M3 muscarinic receptors
IP3, increased intracellular Ca2+
Flow of saliva is modulated by both parasympathetics and sympathetic innervation, and both stimulate salivary secretion.
Sympathetic innervation originates on T1-T3 and synapses on what ganglion?
The postganglionics extend into periarterial spaces and release NE on what receptor found on acinar and ductal cells?
What is the second messenger?
Superior Cervical ganglion
Beta-adrenergic
cAMP
What are the 4 factors that increase the parasympathetic input on salivary glands?
What are the 3 factors that decrease the parasympathetic input on salivary glands?
Increase
Food, smell, nausea, conditioned reflexes
Decrease
Dehydration, fear, sleep
How do ADH and aldosterone modify the composition of saliva?
A. Increase [Na] and decrease [K]
B. Decrease [Na] and [K]
C. Increase [Na] and [K]
D. Decrease [Na] and increase [K]
Decrease [Na] and increase [K]
The gastric mucosa is divided up into the oxyntic gland area and pyloric gland area. Which of the following is true of the oxyntic gland? (Bonus: change the ones describing pyloric gland area to what would be true of the oxyntic gland area)
A. Houses mainly G cell and Mucous neck cells
B. Located in the distal 20% of the stomach (antrum)
C. Secretes HCl from parietal cells
D. Synthesizes and releases gastrin
Secretes HCl
- houses mainly chief cells and parietal cells
- found in the proximal 80% of the stomach (fundus and body)
Which of the following determines the maximal secretory rate of HCl?
A. The pH of the stomach
B. Number of parietal cells
C. Concentration of pepsinogen needed to be converted to pepsin
D. Whether or not we want the gastric contents to be acidified to pH 1-2
Number of parietal cells
Which of the following cells secretes mucus, HCO3 and pepsinogen?
A. Parietal Cells
B. G cells
C. Mucus cells
D. Chief cells
Mucus cells
HCl is formed in the villus like membranes of the canaliculi, and secreted via gastric parietal cells. Transport mechanisms exist in the apical and basolateral membrane of the parietal cells to create a net secretion of HCl on the apical side, and a net absorption of HCO3 on the basolateral side.
What transport mechanisms are found on the apical (lumen)side?
What transport mechanisms are found on the basolateral (blood side) that create the alkaline tide?
Apical Side
H/K ATPase
Cl- channels
- this is the side HCl is secreted, so what would you think would be there
Blood Side
Na/K ATPase
Cl/HCO3 exchanger
NOTE: parietal cells also contain carbonic anhydrase
Omerprazole is used to treat ulcers becayse it reduces H+ secretion. Omerprazole does this by inhibiting which of the following transport mechanisms?
A. apical H/K ATPase
B. apical Cl channel
C. Basolateral Na/K ATPase
D. Basolateral Cl/HCO3 exchanger
apical H/K ATPase
This isn’t a question, just facts to read:
Gastric juice can be seen as a mixture of two seperate secretions, Non-Parietal vs. Parietal.
Non-parietal secretions are a constant, low volume basal alkaline secretion, that’s primarily made of Na, Cl, and K at same [] as plasma. HCO3 is secreted at a concentration of 30mEq/L
Parietal secretions are slightly hyperosmotic, and contain about 160 mEq/L of H, and 20 mEq/L of K, with Cl- being the only anion present (no HCO3-). When secretion rate increases, the [] of the electrolytes approach that of a pure parietal secretion.
Non-parietal Secretions
- basal level alkaline secretion
- Na, Cl, K [] same as plasma
- 30 mEq/L HCO3
Parietal Secretions
- hyperosmotic
- 160 mEq/L H
- 20 mEq/L K
- no HCO3, only Cl-
- increase secretion rate makes it more pure
There is a passive feedback mechanism regulating HCl secretion. Which of the following correctly describes it?
A. Increase in pH inhibits gastrin release causing HCl scecretion to decrease
B. Decrease in pH inhibits gastrin release causing HCl secretion to decrease
C. Decrease in pH inhibits gastrin release causing HCl secretion to increase
D. All of the above are made up
Decrease in pH inhibits gastrin release causing HCl secretion to decrease
All of the following hormones stimulate Gq pathway causing the release of IP3/Ca++ second messenger system, EXCEPT which of the following that stimualtes the Gs pathway and uses cAMP 2nd messenger system?
A. Ach
B. Histamine
C. Gastrin
D. None of the above
Histamine
All of the following drugs inhibit H+ secretion by tageting certain receptors. Which of the following is considered a dirty block because it blocks muscarinic receptors and thus blocks direct and potentiated effects of Ach?
A. Atropine
B. Cimetidine
C. Omerprazole
Atropine
Which of the follwoing hormones gets released into systemic circulation and comes back to bind to cholecystokinin B receptor?
A. Histamine
B. Gastrin
C. Ach
D. Serotonin
Gastrin
Atropine blocks the direct pathway of vagal stimulation for HCl secretion from parietal cells, but it does not block the indirect pathway for gastrin secretion from G cells. Why is atropine unable to block vagal stimulation’s indirect pathway?
A. Vagus N. is too strong
B. GRP is the neurotransmitter not Ach for G cells
C. Luck of the draw
D. Idk any good alteranatives
GRP is the neurotransmitter not Ach for G cells
Somatostatin is released as a negative feedback regulation on gastrin. What mechanism allows more gastrin productivity, despite the fact that gastrin is normally released with somatostatin?
Vagal activation of gastrin also inhibits somatostatin release
T/F: The rate of secretion of HCl is also regulated by the interactions among histamin, Ach, and gastrin
True
Histamine potentiates the actions of Ach and gastrin
Ach potentiates the actions of histamine and gastrin
potentiation: combined response of 2 stimulants is stronger than the sum of their indivdual responses
Which of the following is used to treat duodenal and gastric ulcers as well as gastroesophageal reflux disease?
A. Cimetidine
B. Omerprazole
C. Atropine
D. Acetominophin
Cimetidine
Which of the following phases of gastric secretion is abolished by a vagotomy?
A. Cephalic Phase
B. Gastric Phase
C. Intestinal Phase
Cephalic Phase
- this phase involves Vagus N. stimulation of Ach on M3 and GRP on G cells
Which of the following phases of gastric HCl secretions is stimlated by distention and the breakdown of proteins, AAs, and small peptides? Bonus: what mechanisms are involved in this phase?
A. Cephalic Phase
B. Gasric Phase
C. Intestinal Phase
Gasric Phase
- Indirect/Direct Vagal stimulation
- Local reflexes
- Gastrin-Histamine stimulation
Look at this chart
Look at it again if you can’t explain it
T/F: Decrease pH, somatostatin, and prostaglandins all inhibit HCl secretion
True
PEpsinogen is secreted from chief and mucus neck cells when gastric pH is what value?
A. pH >5
B. pH < 5
C. pH <8
D. pH > 8
pH < 5
What is the optimal pH for pepsinogen secretion?
What is the pH for it to be reversibly inhibited?
What is the pH for it to be reversibly inactivated?
Optimal: 1.8-3.5
Reversible: 3.5-5.0
Irreversible: 7-8
What are 2 common causes of Pernicious anemia where less IF or low uptake of B12 occurs?
- Atrophic gastritis where the chronic inflammation leads to destruction of parietal cells
- immune system attacks IF protein or parietal cells
What is the name of the syndrome where we see a large secretion of gastrin by duodenal or pancreatic gastrinomas? This syndrome also causes a surge in gastrin when secretin is administered?
Zollinger-Ellison Syndrome
What enzyme allows H. pylori to colonize the gastric mucosa, through converting urea to ammonia?
A. Urease
B. Amylase
C. Hyaluronidase
D. Urealyase
Urease
Exocrine pancreas is innervated by ANS, where sympathetic activation inhibits secretions and parasympathetics stimulate secretion.
The postganglionics of sympathetics come from what two locations?
The preganaglionics from parasympathetics are from where?
Celiac and Superior Mesenteric Plexus
Enteric NS
Which of the following cells of exocrine pancrease secretes active amylases, lipases, and inactive proteases?
A. Acinar cells
B. Centroacinar cells
C. Ductal cells
D. None of the above
Acinar cells
Which of the following cells of exocrine pancrease secretes HCO3 rich fluid that alkalizes secretions of acinar cells?
A. Acinar cells
B. Centroacinar cells
C. Ductal cells
D. B and C
B and C
Centroacinar cells
Ductal cells
The ductal cells modify the initial pancreatic secretions via transport mechanisms that yield a net result of HCO3 secretions, and net absorption of H+.
What are the 2 transport mechanisms on the apical membrane?
What are the 2 transport mechanisms on the basolateral membrane?
Apical
Cl/HCO3
CFTR Cl channel
Basolateral
Na/K ATPase
Na/H exchanger
The pancreatic secretions is divided into the following 3 phases. Which of the following phases is responsible for about 80% of secretions and is stimulated by enzymes and aqueous solutions?
A. Cephalic phase
B. Gastric Phase
C. Intestinal phase
Intestinal phase
T/F: The Cephalic and Gastric phase of pancreatic secretions produce mainly enzymatic secretions
True
In regulation of pancreatic secretions, ______ induces the release of enzymes into the duodenum and ____ induces the release of HCO3.
In regulation of pancreatic secretions, CCK induces the release of enzymes into the duodenum and secretin induces the release of HCO3.
During the intestinal phase the presence of amino acids (F,W,M) and peptides stimulates I cells to release what substance that then binds to acinar cells to release IP3/Ca?
A. Secretin
B. Somatostatin
C. CCK
D. None of the aboce
CCK
During the intestinal phase, H+ stimulates S cells to release what substance that would then bind ductal cells and releaese cAMP and release aqueous secretions?
A. Secretin
B. Somatostatin
C. CCK
D. None of the above
Secretin
In the intestinal phase of HCl secretion stimulates acid secretion via which of the following mecahnisms?
A. Vagus nerve releases GRP to release gastrin and act on parietal cells
B. Gastrin released from gastric G cells acting on parietal cells
C. Gastrin released from intestinal G cells acting on parietal cells
D. A and B
E. B and C
Gastrin released from intestinal G cells acting on parietal cells
Which of the following conditions would you suspect in a patient that has a deficiency in intrinsic factor?
A. Decreased pesin secretion
B. Achlohydria
C. Increased coffee intake
D. Increased NSAID use
Achlohydria
- no HCl production
Which of the following are you most likely to see in a patient with a duodenal ulcer?
A. Decreased H+ and increased gastrin levels
B. Increased H+ and gastrin levels
C. Decreased H+ and gastrin levels
D. None of the above
Increased H+ and gastrin levels
Understand the relationship b/w Cystic fibrosis and the pancreas
- Asociated with loss of HCO3 secretion
- decreased pH prematurely activates enzymes leading to pancreatitis
