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40 Cards in this Set
- Front
- Back
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What do parietal cells produce? |
Gastric acid (HCl) Intrinsic factor |
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Intrinsic factor is required for absorption of which vitamin? |
B12 |
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What do enterochromaffin-like (ECL) cells produce? |
Histamine |
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What do chief cells produce? |
Pepsin(ogen), gastric lipase |
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What do D cells produce? |
Somatostatin (inhibits acid) |
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What do G cells produce? |
Gastrin |
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What do neck cells produce? |
Mucus & bicarbonate |
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What makes parietal cells unique? |
- In resting state: intracellular cannaliculi and many mitochondria - Tubulovesicular membranes: extensive sER - Complex system of clefts and canals that are continuous with the lumen of oxyntic gland |
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What activates pepsinogen -> pepsin? |
H+ in gastric juice |
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What results from deficiency in intrinsic factor/vitamin B12? |
Pernicious anemia |
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What ion transporters are brought to the surface of parietal cells upon activation? |
H,K-ATPase Also Cl- and K+ |
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Where are ion transporters sequestered when a parietal cell is resting? |
Tubulovesicular membranes |
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Which ion concentrations increase as the volume of gastric secretion increases? Which decrease? |
Increase: H+, Cl- Decrease: Na+, K+ |
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What enzyme drives H2CO3 -> HCO3- + H+? |
Carbonic anhydrase |
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During active acid secretion into the stomach, excretion of bicarbonate into the blood stream to serve as a buffer is known as.... |
Alkaline tide |
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What is the main messenger of the cephalic phase of acid secretion? What hormones/products does it stimulate? |
Messenger: ACh, gastrin Products: - HCl: parietal cells - Gastrin: G cells - Histamine: ECL cells |
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What helps to initiate the gastric phase of acid secretion? |
Stretch & protein breakdown products (As well as ACh and gastrin) |
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What helps to initiate the intestinal phase/ inhibition of acid secretion? |
1. Neural reflexes: based on duodenal stretch 2. CCK, GIP, secretin 3. Gastrin (secondary to undigested proteins/peptides) |
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What are the 3 main hormonal effectors of gastric acid secretion? |
ACh, gastrin, histamine |
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Which gastric acid secretagogues act through Ca++ as a second messenger? (hormone + R) |
1. Gastrin, CCK2 R 2. ACh, muscarinic R |
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Which gastric acid secretagogues act through cAMP as a second messenger? (hormone + R) |
1. Histamine - Histamine R |
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What does H. pylori use to protect itself from gastric acid? |
Urease: converts urea -> ammonia, which neutralizes gastric acid |
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What disease is characterized by small tumors called gastrinomas? Where are the tumors found? What do they secrete? Ddx? |
Zollinger-Ellison Syndrome Pancreas & duodenum Secrete gastrin Peptic ulcers + high levels of gastrin |
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What types of drugs can be used to treat peptic ulcers? |
1. Histamine receptor antagonists 2. Muscarinic antagonists 3. Proton pump inhibitors |
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What are examples of: 1. Histamine R antagonists 2. Anticholinergics 3. Proton pump inhibitors |
1. Histamine R antagonists - Cimetidine, Ranitide 2. Anticholinergics - Atropin, Oxybutinin, Diphenhrydamine 3. Proton pump inhibitors - Omeprazole |
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What is the progression of pancreatic secretion flow? |
Acinar cells -> lumen of acinus -> intercalated ducts -> intralobular ducts -> interlobular ducts |
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What are the 2 pancreatic ducts? |
Santorini and Wirsung |
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What are the 2 components of pancreatic secretions? From which cells? |
1. Pancreatic enzymes - acinar cells 2. Fluids and electrolytes - ductal cells |
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With increased flow of pancreatic juice, which electrolyte is increased? Which is decreased? Which stay the same (2)? |
HCO3- increased* Cl- decreased* Na+, K+ same
*because of bicarb-Cl exchanger
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A. Which ion exchanger provides bicarb to the cell from the basolateral membrane? B. Which ion exchanger provides bicarb to the lumen from the apical membrane? C. What channel maintains the necessary gradient for B? |
A. Na/HCO3 cotransporter B. Cl/HCO3 antiport C. CFTR (Cl- channel) |
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How does Na+ and water get from the blood/interstitium to the lumen of the pancreatic ducts? |
Diffuses between cells |
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What transporter gets Cl- into the pancreatic ductal cells, allowing Cl- to move into the lumen through the CFTR channel? |
NCCK (Na/Cl/K contransporter) |
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What paracrine hormone inhibits pancreatic enzyme secretion? |
Somatostatin |
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What hormones/substances increase pancreatic enzyme secretion via cAMP second messenger? |
VIP, secretin |
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What hormones/substances increase pancreatic enzyme secretion via Ca++ second messenger? |
GRP/gastrin, ACh, *CCK* |
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What hormones/substances increase pancreatic bicarb secretion by the ductal cells? |
1. SECRETIN (most potent) via PKA 2. ACh via Ca++ |
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What mechanisms protect acinar cells from auto digestion? |
1. Packaging of proteins in zymogens 2. Sequestering in secretory granules 3. Protease inhibitors in zymogen granules 4. Packaging at low pH 5. Non-digestive proteases |
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How is trypsin activated? Chymotrypsin? |
Trypsinogen -> trypsin by brush border enterokinase
Chymotrypsinogen -> chymotrypsin by trypsin |
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What is the main pancreatic enzyme to digest: 1. starch/carbs 2. proteins 3. fats |
1. starch/carbs: amylase 2. proteins: protease 3. fats: lipase |
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What are the risk factors for pancreatitis? Symptoms? |
- Gallstones, alcohol abuse, toxins, hypertriglyceridemia, Cystic Fibrosis - Horrible pain radiating like a belt |
