Upper GI anatomy

Question 1

Name the 3 important muscles of the oesophagus

Answer 1

cricopharyngeus/upper oesophageal sphincter

oesophagus

lower oesophageal sphincter

Question 2

What are the layers of the oesophageal wall?

Answer 2

out–>in

adventitia
muscularis - longitudinal layer, circular layer
submucosa
mucosa

Question 3

What does contraction of the circular muscle of the oesophagus cause?

Answer 3

increase in luminal pressure

Question 4

What does contraction of the longitudinal muscle of the oesophagus cause?

Answer 4

shortening

Question 5

What can cause increase in lower oesophageal sphincter pressure?

Answer 5

protein
carbohydrate
(refluxed) acid
alpha-agonists
beta-blockers
cholinergics
metoclopramide
domperidone

Question 6

What can cause decrease in lower oesophageal sphincter pressure?

Answer 6

alcohol
anticholinergics
chocolate
fat
caffeine
citrus
garlic
tomato
beta-agonists
calcium channel blockers
dopamine
nicotine
nitrates
progesterone
oestrogen
tricyclic antidepressants

Question 7

What does the stomach do?

Answer 7

reservoir
mixing
secretion
digestion
defence
absorption

Question 8

Name some gastric secretions

Answer 8

gastric (hydrochloric) acid
pepsinogen
intrinsic factor
gastrin
leptin
ghrelin
somatostatin
histamine

Question 9

Name some cells of the stomach and what they produce

Answer 9

parietal cell - acid, IF
chief cell - pepsinogen, leptin
enterochromaffin-like cell - histamine
G-cell - gastrin
D-cell - somatostatin
epithelial cells - mucus
progenitor cells

Question 10

What are the phases of gastric secretion?

Answer 10

cephalic - thought/ingestion of food - stimulation

gastric - food in stomach - stimulation

intestinal - food in small intestine - initial stimulation, later inhibition

Question 11

Gastrin function

Answer 11

main physiological stimulant of gastric acid secretion

Question 12

When is gastrin release inhibited?

Answer 12

when pH<3

Question 13

What controls gastrin secretion?

Answer 13

somatostatin
somatostatin secretion declines as pH>3

Question 14

Describe the parietal-ECL-D cell unit

Answer 14

functional cellular unit of acid secretion
located in gastric body
direct activation of parietal cell
indirect activation by ECL-cell secreted histamine
paracrine inhibition by somatostatin

Question 15

Name the main stimulants of acid secretion

Answer 15

acetylcholine
gastrin
histamine
(activation of multiple pathways is synergistic)

Question 16

Name the main inhibitors of acid secretion

Answer 16

somatostatin (inhibits gastrin + histamine secretion, inhibits parietal cell directly)
PGE2 (inhibits parietal cell directly)

Question 17

What diseases cause excess acid secretion?

Answer 17

excess gastrin:
- gastrinoma (Zollinger-Ellison syndrome)
- short bowel syndrome
- non-gastrin ZES
- G cell hyperfunction
- H. Pylori

excess histamine:
- systemic mastocytosis

hypercalcaemia

Question 18

What diseases cause too little acid secretion?

Answer 18

inflammation +/- atrophy of gastric body:
- autoimmune gastritis
- H.Pylori gastritis

Iatrogenic:
- Drugs
- vagotomy

associated with infectious diarrhoea and gastric adenocarcinoma