physiology 2 -GI secretory products-Locations of GI secretory cells-Gastric parietal cell (not in book)

Question 1

In pernicious anemia, destruction of gastric ____ cells leads to deficiency of ____ required for vitamin B12 uptake in the ____.

Answer 1

Parietal; intrinsic factor; terminal ileum

Question 2

A patient has chronic abdominal pain and numerous peptic ulcers refractory to proton pump inhibitors. What tumor should be suspected?

Answer 2

Gastrinoma, which is a gastrin-secreting tumor that results in high levels of acid secretion

Question 3

Describe how pepsin is activated.

Answer 3

It is activated by vagal stimulation of increased acid output, which cleaves inactive pepsinogen to active pepsin

Question 4

What is the primary role of pepsin? What cells secrete it, and where are these cells found?

Answer 4

Functions in protein digestion; secreted by the gastric chief cells

Question 5

Bicarbonate is secreted by ____ cells and ____ glands; its function is to ____ acid.

Answer 5

Mucosal; Brunner; neutralize

Question 6

A patient with a gastrinoma can be expected to also have excessive activation of which pro-enzyme?

Answer 6

Pepsinogen (activated by acid, the release of which is stimulated by gastrin)

Question 7

Produced by these cells found in this organ, pepsinogen becomes pepsin when there is a high acid content in the stomach.

Answer 7

Chief cells of the stomach

Question 8

Increased levels of what three molecules cause parietal cells to release gastric acid?

Answer 8

Acetylcholine, histamine, and gastrin

Question 9

Decreased levels of which hormones will cause parietal cells to secrete gastric acid?

Answer 9

Somatostatin, GIP, prostaglandin, secretin

Question 10

Where is bicarbonate typically trapped in the GI system?

Answer 10

Bicarbonate is trapped in the mucus that covers the gastric epithelium.

Question 11

A patient has vitamin B12 deficiency. What part of the GI system could be damaged, impacting vitamin B12 levels?

Answer 11

Parietal cells of the stomach or the terminal ileum (the latter is where vitamin B12 is absorbed as a complex with intrinsic factor)

Question 12

Where are bicarbonate-secreting mucous glands found? What about bicarbonate-secreting Brunner glands?

Answer 12

Stomach, duodenum, salivary glands, pancreas; duodenum

Question 13

A patient presents with pallor and macrocytic anemia. She has atrophic gastritis and thus makes antibodies acting at which stomach cells?

Answer 13

Parietal cells (this is pernicious anemia)

Question 14

HCl and intrinsic factor are released by ____ cells in the ____ of the stomach.

Answer 14

Parietal; body

Question 15

A patient who received atropine would have ____ (increased/decreased) production of intrinsic factor

Answer 15

Decreased

Question 16

____ is produced by chief cells in the ____ of the stomach.

Answer 16

Pepsinogen; body

Question 17

Name three types of secretory cells found in the duodenum and their associated products

Answer 17

I cells (cholecystokinin), K cells (glucose-dependent insulinotropic peptide [GIP], S cells (secretin)

Question 18

Somatostatin is made by ____ cells in the ____ of the stomach

Answer 18

D, antrum

Question 19

What influence does atropine have on the gastrointestinal secretory cells?

Answer 19

Blocks vagal stimulation of parietal cells only

Question 20

Gastrin stimulates the production of which two substances?

Answer 20

Histamine (causes acid secretion) and intrinsic factor

Question 21

Name four substances that are secreted directly into the lumen of the stomach

Answer 21

Mucus, pepsinogen, intrinsic factor, and HCl

Question 22

Does gastrin stimulate the basal or apical surface of the parietal cells?

Answer 22

Basal surface (gastrin is secreted into circulation to stimulate enterochromaffin-like and parietal cells)

Question 23

What cells does gastrin act on to increase acid secretion through histamine release?

Answer 23

Enterochromaffin-like cells

Question 24

The proton pump of parietal cells can be found on which side of the cell?

Answer 24

The luminal side

Question 25

The proton pump of the parietal cells pumps ____ into the cell and sends ____ out of the cell and into the lumen.

Answer 25

Potassium ions; protons

Question 26

A patient in the United States with raw epigastric pain after eating might get relief with which class of medication?

Answer 26

Proton pump inhibitors (H2 receptor blockers are also useful, but most guidelines recommend starting with a PPI first)

Question 27

How does acetylcholine stimulate acid production by parietal cells?

Answer 27

It activates an M3 receptor on the cells that directly stimulates acid secretion through the proton pump via a G-protein cascade

Question 28

In what two ways does gastrin stimulate acid production by parietal cells?

Answer 28

Gastrin primarily stimulates histamine production by ECL cells, and binds directly to parietal cell cholecystokinin (CCKB) receptors

Question 29

Carbonic anhydrase is an enzyme that converts carbonic acid to what two molecules in the parietal cell?

Answer 29

Carbon dioxide and water

Question 30

As a proton leaves the parietal cell on the luminal side, bicarbonate leaves the cell via the basolateral side and causes what effect?

Answer 30

The alkaline tide, a transient increase in interstitial pH secondary to gastric acid production/bicarbonate secretion from the parietal cell

Question 31

What is the second messenger that is used in histamine-induced acid secretion?

Answer 31

cAMP, stimulated by the H2 receptor

Question 32

What substances inhibit acid secretion by the parietal cells?

Answer 32

Prostaglandins, somatostatin

Question 33

Each of these pathways has an inhibitory drug to decrease acid release, except for which one? (ACh to M3, gastrin to CCKB, histamine to H2)

Answer 33

Gastrin to CCKB receptor, as gastrin has no clinically useful pharmacologic inhibitor

Question 34

A woman with too much gastric acid takes a drug that decreases parietal cell cAMP levels. By what pathway does this drug act?

Answer 34

Acts via the Gi pathway to decrease parietal cell cAMP levels and lower acid secretion (the drug is misoprostol, a prostaglandin analog)