GI secretions: gastric, pancreatic and drugs for peptic ulcer disease

Question 1

What are the gastric secretory products?

Answer 1

HCl; intrinsic factor; pepsinogen; gastrin; mucus

Question 2

What, where and stimulus of HCl secretion?

Answer 2

pareital cells;
body/fundus of stomach;
=>gastrin; ACh (from vagus); histamine

Question 3

What, where and stimulus of intrinsic factor secretion?

Answer 3

pareital cells;
body/fundus of stomach;
=>gastrin; ACh (from vagus); histamine

Question 4

What, where and stimulus of pepsinogen secretion?

Answer 4

chief cells;
body/fundus of stomach;
=> ACh (from vagus); gastrin; HCl

Question 5

What, where and stimulus of gastrin secretion?

Answer 5

G cells;
Antrum;
=> small peptides/amino acids; vagus (via GRP); stomach distension

Question 6

What, where and stimulus of mucus secretion?

Answer 6

mucous cells;
entire stomach;
ACh (from vagina)

Question 7

inhibitors of HCl and intrinsic factor?

Answer 7

• Low pH inhibits (by inhibiting gastrin)
• prostaglandins
• chyme in duodenum (via GIP and secretin)

Question 8

inhibitors of pepsinogen

Answer 8

H+ (via somatostatin)

Question 9

inhibitors of gastrin

Answer 9

H+ (via somatostatin)

Question 10

action of mucus

Answer 10

forms gel on mucosa to protect mucosa from HCl and pepsin;

traps HCO3 to helps neutralize acid

Question 11

action of gastrin

Answer 11

• increase HCl secretion (parietal cells)
• increase pepsinogen secretion (chief cells)
• increase histamine secretion by ECL cells

Question 12

action of pepsinogen

Answer 12

• Digests up to 20% of proteins

- converted to pepsin w/ low pH and pepsin (autocatalytic)

Question 13

action of intrinsic factor

Answer 13

• necessary for VITAMIN B12 absorption by ileum;

- forms complex w/ vitamin B12

Question 14

action of HCl

Answer 14

• kills pathogens

- activates pepsinogen to pepsin

Question 15

What are the 3 primary triggers of H+ secretion?

Answer 15

• ACh (from vagus) => M3 muscarinic receptor
• Histamine => H2 histamine receptor
• Gastrin => unidentified receptor

Question 16

Describe the 3 steps in gastric H+ secretion

Answer 16

1) parietal cell=> CO2, H2O converted to H+ and HCO3 via carbonic anhydrase
2) H+ secreted into lumen of stomach by H-K ATPase => Cl- is secreted w/ H+
3) HCO3 absorbed into bloodstream in exchange for Cl-

Question 17

What is alkaline tide?

Answer 17

after meal=> enough H+ secreated to raise pH of systemic blood and turn urine alkaline => alkaline tide

Question 18

3 phases of gastric secretion

Answer 18

cephalic, gastric, intestinal phases

Question 19

how does cephalic phase of gastric secretion occur?

Answer 19

“senses” increase gastric secretion via PANS => 30% responsible for H+ secretion

Question 20

how does gastric phase of gastric secretion occur?

Answer 20

-food in stomach increases secretion;
-proteins, peptides, alcohol, caffeine cause *gastrin release
-gastric distention initiates vagovagal reflexes
=>60% of acid secretion

Question 21

how does intestinal phase of gastric secretion occur?

Answer 21

-protein digestion products in duodenum stimulate gastrin secretion;
-absorbed amino acids act to stimulate H+ by parietal cells
=>less than 10% of acid secretion due to meal

Question 22

What are the drug classes for peptic ulcer disease?

Answer 22

antacids;
H2 antagonists; PPI;
mucosal protective agents; antibiotics

Question 23

primary antacid agents

Answer 23

MgOH; AlOH; CaOH

Question 24

What are the effects of antacids?

Answer 24

Mg=> laxative effect

AlOH=> constipating effect

Question 25

Agents of H2 antagonists?

Answer 25

*cimetidine; | ranitidine; famotidine; nizatidine

Question 26

How does cimetidine work and what type of physio effects are associated?

Answer 26

inhibits hepatic drug metabolizing enzymes antiandrogen effects

Question 27

Agents of PPI

Answer 27

*omeprazole | lansoprazole; esomeprazole; pantoprazole; rabeprazole

Question 28

How do PPI work?

Answer 28

irreversibly inactivate H-K ATPase => block H+ secretion

Question 29

What disease do PPI work well in?

Answer 29

PUD, ZE syndrome; GERD

Question 30

mucosal protective agents

Answer 30

* Sucralfate | - misoprostol

Question 31

action of sucralfate

Answer 31

polymerizes in stomach and forms protective coating over ulcer beds

Question 32

when is misoprostol used?

Answer 32

PGE1 derivative used for peptic ulcers caused by NSAIDs

Question 33

What and why are the antibiotics used in peptic ulcer disease?

Answer 33

macrolides; metronidazole; tetracyclines => treat H. pylori

Question 34

What are the exocrine secretions of pancreas caused by?

Answer 34

acinar cells and ductal cells

Question 35

How do acinar cells produce exocrine secretions?

Answer 35

contain numerous enzyme-containing granules in cytoplasm

Question 36

how do ductal cells produce exocrine secretions?

Answer 36

secrete HCO3

Question 37

How do exocrine secretions reach duodenum?

Answer 37

pancreatic duct

Question 38

What is the fxn of HCO3 in duodenum?

Answer 38

* neutralizes HCl in chyme entering stoamch | - deactivates pepsin

Question 39

What causes an increase in HCO3 production?

Answer 39

H+ entering duodenum *=> S cells secrete secretin => secretin acts on pancreatic ductal cells to increase HCO3 production

Question 40

What enzyme is responsible for HCO3 production? and where does this occur?

Answer 40

ductal cells contain *carbonic anhydrase

Question 41

How does HCO3 get into the blood?

Answer 41

exchange for Cl-

Question 42

If a person goes and eats a lot of Gus's fried chicken, what is responsible for this digestion?

Answer 42

*CCK released by I cells in response to meals w/ small peptides, amino acids and fatty acids => stimulate pancreatic enzyme secretion

Question 43

What is the role of ACh in pancreatic enzymes?

Answer 43

via vagovagal reflexes=> stimulates enzyme secretion; potentiates action of secretin

Question 44

What provides protection of pancreatic acinar cells against self-digestion?

Answer 44

* proteolytic enzymes are secreted as inactive precursors | * produce enzyme inhibitors

Question 45

What is the role of enzyme inhibitor production wrt protection of acinar cells?

Answer 45

inactivate trace amounts of active enzyme formed w/in

Question 46

What is the role of proteolytic enzymes being secreted as inactive precursors for acinar cell protection?

Answer 46

these enzymes get activated in gut lumen

Question 47

What are pancreatic enzymes that are not pro-enzymes so acinar cells are not protected?

Answer 47

ribonucleases; amylase; lipase

Question 48

What are the proteases of pancreas and associated reaction catalyzed?

Answer 48

trypsin=> proteins to peptides; chymotrypsin=> proteins to peptides; carboxypeptidase => peptides to amino acids

Question 49

What are the polysacchardases of pancreas and associated reaction catalyzed?

Answer 49

amylase => starch/glycogen to maltose, maltotriose, alpha-limit dextrins

Question 50

What are the lipases of pancreas and associated reaction catalyzed?

Answer 50

* phospholipases A & B=> phospholipids to phosphoate, FA, glycerol * esterases=> cholesterol esters to free cholesterol and FA * TAG lipases=> Triglycerides to FA and monoglycerides

Question 51

What are the nucleases of pancreas and associated reaction catalyzed?

Answer 51

* ribonuclease=> RNA to ribonucleotides | * deoxyribonuclease=> DNA to doxyribonucleotides