*Physiology (gastric gland secretions)

Question 1

What type of cells are present in the pyloric gland area (antrum)? (2)

Answer 1

D cells

G cells

Question 2

What type of cells are present in the oxyntic mucosa in fundus and body of the stomach? (3)

Answer 2

Chief cell
Enterochromaffin-like cell
Parietal cells

Question 3

What do D cells secrete?

Answer 3

Somatostatin

Question 4

What do G cells secrete?

Answer 4

Gastrin

Question 5

What do chief cells secrete?

Answer 5

Pepsinogen

Question 6

What do enterochromaffin-like cells secrete?

Answer 6

Histamine

Question 7

What do parietal cells secrete?

Answer 7

Hydrocholric acid

Intrinsic factor

Question 8

What does pepsinogen released from chief cells do?

Answer 8

Precursor of pepsin which when activated by HCl becomes pepsin

Question 9

What does histamine released from enterochromaffin-like cells do?

Answer 9

Stimulates HCl secretion

Question 10

What does hydrochloric acid secreted from parietal cells do?

Answer 10

Activates pepsinogen to pepsin
Denatures protein
Kills most micro-organisms ingested

Question 11

What does intrinsic factor released from parietal cells do?

Answer 11

Binds vitamin B12 allowing adsorption in the terminal ileum

Question 12

What does somatostatin released from D cells do?

Answer 12

Inhibits HCl secretion

Question 13

What does gastrin released from G cells do?

Answer 13

Stimulates secretion of HCl acid

Question 14

What is the full name of the proton pump?

Answer 14

H+/K+ATPase (pumps H+ out and K+ in)

Question 15

Where does the Cl- come from that makes HCl?

Answer 15

It is pumped into the cell via the Cl-/HCO3- antiporter and is then pumped into the caniliculis via a Cl- channel

Question 16

What 3 regulatory molecules stimulate HCl secretion?

Answer 16

ACh
Histamine
Gastrin

Question 17

What receptor does ACh stimulate acid secretion via?

Answer 17

M3

Question 18

How does ACh stimulate secretion of HCl?

Answer 18

When M3 is activated, it stimulates the proton pump and hence secretion of H+
It also acts on M1 receptors on Enterochromafin like cells causing the release of histamine

Question 19

How does histamine stimulate secretion of HCl?

Answer 19

It acts on an H2 receptor on the membrane of parietal cells increasing the activation of the proton pump

Question 20

How does gastrin increase secretion of HCl?

Answer 20

It stimulates gastrin receptors which increase activation of the proton pump
Gastrin also stimulates ECL cells increasing histamine release

Question 21

What inhibits HCl release? How?

Answer 21

Somatostain inhibits the release of gastrin and histamine
Prostoglandin E2 stimulates prostoglandin receptors on parietal cells inhibiting the action of ACh, gastrin and histamine

Question 22

What is a secretagogue?

Answer 22

A substance that causes another substance to be secreted

Question 23

How are proton pumps activated? e.g. by histamine, ACh and gastrin

Answer 23

Causes the insertion of the proton pump into the apical membrane - through protein kinases

Question 24

What are the 3 phases of gastric secretion?

Answer 24

Cephalic (before food reaches the stomach)
Gastric (when food is in the stomach)
Intestinal (after food has left the stomach)

Question 25

What happens during the intestinal stage of gastric secretion?

Answer 25

Factors originating from the small intestine switch off acid secretion

Question 26

What effects do prostaglandins have locally in the stomach?

Answer 26

Reduce acid secretion
Increase mucus and bicarbonate secretion
Increase mucosal blood flow

Question 27

What is a peptic ulcer?

Answer 27

An area where the mucosa is exposed to HCl and pepsin

Question 28

What is Zollinger-Ellison syndrome?

Answer 28

Rare, gastrin producing tumour