Gastric Secretion

Question 1

What is the function of the fundus of the stomach?

Answer 1

Storage

Question 2

What is the function of the antrum of the stomach?

Answer 2

To grind food and to make gastrin

Question 3

What is the function of the body of the stomach?

Answer 3

Make HCL, make pepsinogen, make intrinsic factor, make mucus and store

Question 4

What secreting cells are found in the mucosa of the stomach?

Answer 4

Chief cells (pepsingogen), mucus neck cells (mucus) and parietal cells (HCL and intrinsic factor)

Question 5

Explain - in outline - how a PH2 HCL acid is made in the stomach

Answer 5

CO2 from the blood diffuses into the enterocyte
The C02 binds with H20 in a reaction catalysed by carbonic anhydrase
This produces H2C03
H ion leaves on apical surface via the H / K proton pump
HC03 leaves on the basolateral membrane via HC03 / CL channel
The osmotic gradient created allows for the movement of water into the apical surface

Question 6

How does gastrin work?

Answer 6

Secreted into blood stream (endocrine) and ends up back at the stomach. Binds to its receptor and causes intraceullular Ca increase. Activates protein kinases which cause activation of proton pump.

Question 7

How does histamine work?

Answer 7

Secreted locally and acts locally (paracrine). Works on H2 receptors. Causes activation of GS and adenyl cyclase activation. Causes ATP phosphorylation to CAMP. Causes activation of the proton pump.

Question 8

How do prostocyclins work?

Answer 8

Inhibit the proton pump by being coupled to GI

Question 9

How does acetylcholine work?

Answer 9

Binds to muscarinic receptors

Question 10

Describe how gastric acid secretion may be regulated in the cephalic phase (the thinking of eating phase)

Answer 10

The smell, sight and taste of food do a lot to the system
The parasympathetic system is activated
This in turn causes the release of acetylcholine and gastrin from G cells
This causes acid production
As well as this, gastrin ands acetyl choline cause the release of histamine from ECL cells which in turn also increase a cid production

Question 11

Describe how gastric acid secretion may be regulated in the gastric phase

Answer 11

stomach distention causes vagal and enteric stimulation
This causes the release of acetylcholine which in turn causes the production of stomach acid

Peptides cause the release of gastrin from the G cells and this stimulates acid production

Gastrin / acetylcholine cause the release of histamine that causes an increase in stomach acid