Gastric Secretions / Peptic Ulcer Disease

Question 1

describe the anatomy of the cardia

Answer 1

transition zone from squamous to columnar epithelium

protects surface of stomach from corrosive gastric contents + previous reflux shallow gastric pits: surface mucus cells

Question 2

what kind of cells are found in the fundus and body?

Answer 2

deep gastric pits: contain surface and neck mucus cells, PARIETAL cells, CHIEF cells, endocrine cell (ECL cells, D cells)

Question 3

main functions of fundus and body

Answer 3

accommodation gastric acid secretion

Question 4

function of the antrum

Answer 4

mixing, grinding, sieving ingested particles regulation of gastric secretory function via gastrin/somatostatin intermediate gastric pits: surface and neck mucus cells, endocrine cells

Question 5

surface cell and neck cells: product and function

Answer 5

products: mucus, HCO3-, trefoil peptides
function: lubrication, protection

Question 6

parietal cells: product and function

Answer 6

product: H+, intrinsic factor
function: protein digestion, binding of cobalamin, protection from bacteria

Question 7

chief cells: product and function

Answer 7

product: pepsinogen, gastric lipase
function: protein digestion, TG digestion

Question 8

endocrine cells: product and function

Answer 8

product:

• gastrin from G-cells
• histamine from ECL cells
• somatostatin from D-cells

function: regulation of acid secretion

Question 9

what type of cell is this? describe some characteristics

Question 10

parietal cell: describe resting and stimulated states

Answer 10

resting:

• gastric acid pump is present in tubulovesicles but inactive

stimulation by ACh, Gastrin, Histamine

• gastric acid pump in tubulovesicles is incorporated into the canaliculus and becomes active
• action: exchanges H for K, creates HCl to be released into lumen

Question 11

what stimulates the parietal cell?

Answer 11

acetylcholine

gastrin/CCK - unclear importance

histamine - most important

Question 12

diagram gastric acid secretion

Answer 12

Question 13

describe acid/electrolyte composition of gastric juice in resting and stimulated states

Answer 13

resting: non-parietal, resembles interstital fluid w/ high Na
stimulated: parietal, high H+ content

Question 14

how does the stomach protect itself from acid?

Answer 14

mucus: glycoproteins w/ disulfide bridges –> mucus gel

made through physical stimualtion and ACh stim by mucus neck cells and mucus surface cells

Question 15

what agents disrupt gastric mucosal barrier?

Answer 15

weak acids (aspirin), alcohols (ethanol), NSAIDs , bile salts

Question 16

overview of phases of acid secretion stimulation

• name
• stimulus
• % response to a meal

Answer 16

1. interdigestive
2. cephalic
3. gastric
4. intestinal

Question 17

describe what happens in the cephalic phase

Answer 17

• sight, smell and taste of food –> excites central vagus efferents
• Ach released to enteric nervous system –> stimulates…
  
  • parietal cells
  • chief cells (a little) - pepsinogen
  • ECL to produce histamine –> local action
  • G cells
• vagal efferents tim G cells in neuroendocrine fashion via GRP - STRONG effect

Question 18

describe what happens in the gastric phase

Answer 18

• food causes increase in pH –> increased gastrin release
• AA and proteins stimulate G-cells to release gastrin
• fundal distension –> increase in parietal cell secretion of acid (vagally mediated)

Question 19

why do ulcer pts have relief of pain after meals, but pain returns 2 hrs later?

Answer 19

H+ buffered by food, but then acid is secreted in response

Question 20

describe what happens in the intestinal phase of acid secretion

Answer 20

not well understood

• stimulatory factors: AAs in small intestine stim release of gastrin
• inhibitory factors: chyme in upper intestine inhibits gastric acid secretion (maybe via secretin, GIP)

Question 21

alkaline tide

Answer 21

for each H+ secreted into the stomach lumen, HCO3- is secreted into the blood

• HCO3- is used by surface mucus cells to maintain mucus layer and protect enterocytes

Question 22

most likely endoscopy finding in a pt w/ gnawing pain in epigastrium

Answer 22

normal! - 60-90% of the time, pts get ulcer-like symtpoms WITHOUT ulcer = non-ulcre dyspepsia

Question 23

dx of peptic ulcer disease

Answer 23

upper endoscopy

• can exclude cancer, detect H. pylori

Question 24

complications of peptic ulcer disease

Answer 24

hemorrhage

perforation or penetration to adjacent organ (pancreatitis)

gastric outlet obstruction

Question 25

pathogenesis of peptic ulcers

Answer 25

• H. pylori –> chronic superficial gastritis in antrum + intestinalized gastric mucosa + acid hypersecretion (somatostatin suppression —> less inhibition of gastrin release)
• compromised mucosal defense: NSAIDS or H. pyloria –> diffuse superficial antral gastritis
  
  • PGE2 important for maintaining mucosa
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