Parietal Cells and Peptic Ulcers

Question 1

What is the role of parietal cells?

Answer 1

To secrete HCl

Question 2

What is the role of Chief Cells?

Answer 2

To produce pepsinogen/gastric lipase

Question 3

What is the role of G/enteroendocrine cells?

Answer 3

Secretion of Gastrin

Question 4

What do D cells secrete?

Answer 4

Somatostatin

Question 5

Volume and [H+] Concentration of Gastric acid secreted?

Answer 5

2L/day

>150mM

Question 6

How are H+ produced in gastric acid?

Answer 6

H2O + CO2 –> H+ + HCO3- (Parietal cells)

Question 7

How does the H+/K+ ATPase proton pump work?

Answer 7

H+ pumped out to Lumen, K+ into parietal cell (HOPI)

Question 8

How does the proton pump on basal surface of parietal cell?

Answer 8

Cl- transported in, Bicarbonate transported out

Question 9

What is the significance of Cl-, HCO3- exchange?

Answer 9

HCO3- out of cell, increases forward reaction so more H+. Cl- in and then out through luminal surface can combine with H+ to form HCl

Question 10

What are the 4 phases in regulating GA secretion?

Answer 10

1) Cephalic (ON)
2) Gastric (ON)
3) Gastric (OFF)
4) Intestinal (OFF)

Question 11

Stimulation and mechanism of Cephalic Phase?

Answer 11

S: Chewing, smell/sight/taste of food
M: PSNS causes Ach release, acts on parietal cells, triggers gastrin & histamine release, so more acid produced

Question 12

Stimulation and mechanism of Gastric ON Phase?

Answer 12

S: Gastric distension, peptide presence, AA in stomach
M: Gastrin released in response, on parietal cells, histamine released and acts, so more HCl secreted

Question 13

Stimulation and mechanism of Gastric OFF Phase?

Answer 13

S: Low pH in gastric lumen
M: Gastrin inhibited in R2S, making gastrin same. Somatostatin released, inhibiting parietal cells, HCl secretion decreases

Question 14

Stimulation and mechanism of Intestinal Cells?

Answer 14

S: Low pH duodenal lumen, AA and FA in duodenum
M: Enterogastrones 1) Secretin 2) CCK released in R2S, Sec inhibits Gastrin, ^ somatostatin release, HCl secretion V

Question 15

Name the 1) NT 2) Hormone 3) Paracrine Factors 4) Enterogastrones involved in GA secretion?

Answer 15

1) Ach
2) Gastrin
3) Histamine, Somatostatin
4) Secretin, CCK

Question 16

What is a peptic ulcer?

Answer 16

Breach in a mucosal surface

Question 17

What are the 4 defences for GA secretion?

Answer 17

1) Alkaline Mucous
2) Tight junctions between Epithelial cells
3) Replacement of Damaged Cells
4) Feedback Loops

Question 18

What 3 things cause peptic ulcers?

Answer 18

1) Heliobacter pylori
2) NSAIDS
3) Chemical Irritants

Question 19

How does HBP cause peptic ulcers?

Answer 19

1) Lives in gastric mucous and secretes urease
2) Urease BD Urea –>CO2 and NH3, NH3 combines with H+ to form NH4+
3) NH4+ damages gastric epithelium, inflammatory response triggered, mucosal defence reduced

Question 20

How do NSAIDs cause peptic ulcers?

Answer 20

1) Inhibit cycle-oxygenase 1
2) Needed for prostaglandin synthesis, which secrete mucous
3) Less mucous, and mucosal defence reduced

Question 21

Name 2 drugs that can be used to reduce gastric acid secretion.

Answer 21

1. Proton pump inhibitors.

2. H2 receptor antagonists.