Gastric Secretion Prunuske

Question 1

How long does food usually hang out in stomach?

Answer 1

~4 hours

Question 2

Main enzyme in stomach?

Answer 2

Pepsin

Question 3

What part of the stomach is important as a secretion reservoir and is important for acid secretion?

Answer 3

Fundus and body

Question 4

What happens in the antrum?

Answer 4

Mixing and grinding

*Technical word is…Truition

Question 5

Where are the oxyntic/parietal glandular mucosa?

Answer 5

Body

Question 6

What cells secrete pepsinogen?

Answer 6

Chief cells

Question 7

What do parietal (oxyntic) cells secrete?

Answer 7

HCl
Intrinsic factor
Gastroferrin

Question 8

Do parietal cells and chief cells get turned over regularly?

Answer 8

Nope, they are pretty stable!

Question 9

What cells secrete gastrin?

Where are they?

Answer 9

G cells in the Antrum

Question 10

What does gastrin do?

Answer 10

Activates parietal cells in the fundus/body to secrete acid!

Question 11

What are the 2 triggers for gastrin release from G cells?

Answer 11

1. Seeing food or stomach distension causes vagal stimulation causing release of Gastrin-releasing peptide (GRP)
2. Aromatic amino acids in the lumen

Question 12

What 3 things come in to bind to parietal cells to activate acid secretion?

Answer 12

Gastrin
Histamine
Ach

Question 13

What does Atropine do to gastric acid secretion?

Answer 13

Inhibit!

*Its a muscarinic antagonist

Question 14

Where does Histamine get released?

Answer 14

ECL cells

*Another target of gastrin…it binds to them and triggers histamine release!

Question 15

Where are H+/K+ ATPases found in pareital cells?

Answer 15

Tubulo-vesicles

Question 16

What happens to tubulovesicular cells when the parietal cells are stimulated?

Answer 16

They fuse with the canalicular membranes to increase their density at the apical membrane!

Question 17

What is the consequence of your Na+/K+ ATPase being active on basolateral membrane?

Answer 17

Alters electrical membrane potential b/c pumping out 3 Na for every 2 K coming in…going to have low sodium inside these cells.

There are potassium channels on the apical surface

Question 18

What special enzyme is active in parietal cells to generate H+ and Bicarbonate?

Answer 18

Carbonic anhydrase!

Question 19

“Alkaline tide”

Answer 19

Blood in that immediate region is at a higher pH because bicarbonate is being excreted by parietal cells into the bloodstream

Question 20

What organelle is abundant in parietal cells?

Answer 20

Mitochondria!

*Lots of ATP generation needed

Question 21

What do proton pump inhibitors bind?

Answer 21

H+ K+ ATPase

So they directly interfere with H+ ions being pumped into lumen!

Question 22

Where are D cells?

Answer 22

Adjacent to our G cells in the antrum

Question 23

What do D cells release to inhibit G cells?

When are they going to release it?

Answer 23

Somatostatin!

If pH is really low and you don’t need active parietal cells! pH

Question 24

Is there more or less somatostatin released when you eat food?

Answer 24

Less!

Because as food enters the stomach, the pH rises…therefore more gastrin is needed so less somatostatin is released!

Question 25

What do prostaglandins do in parietal cells?

Answer 25

Inhibit cAMP formation **Fill in why this is important

Question 26

Which hormone is secreted due to increase in H+ in duodenum? What does this block the secretion of?

Answer 26

Secretin Histamine by ECL cells

Question 27

What is required for B12 absorption?

Answer 27

Intrinsic factor

Question 28

In what form is pepsinogen secreted?

Answer 28

As a proenzyme *Doesn't become active until it gets to gastric lumen

Question 29

What cells start the process of enzymatic digestion of protein and fat?

Answer 29

Chief cells

Question 30

What two things are positive regulators of chief cell secretion?

Answer 30

ACh | Gastrin

Question 31

What inhibits chief cell secretion?

Answer 31

Secretin

Question 32

What is Zollinger-Ellison Syndrome?

Answer 32

Gastrinoma! GASTRIN-secreting tumor in PANCREAS or SMALL INTESTINE Excess H+ secretion and hyperplasia/hypertrophy of parietal cells *Most patients develop gastric ulcers

Question 33

What is peptic ulcer disease?

Answer 33

Hyperacidity...Deterioration of gastro-mucosal barrier

Question 34

Infection from what organism can cause gastric and duodenal ulcers?

Answer 34

Helicobactor pylori

Question 35

What 2 broad things contribute to ulcers?

Answer 35

Increase in acidity Decrease in protective factors

Question 36

How does H Pylori contribute to ulcers?

Answer 36

Inhibits somatostain so Gastrin is highly active. | Gastrin binds to parietal and ECL cells to increase acidity!

Question 37

What does Achlorhydria mean?

Answer 37

Reduced acid secretion

Question 38

What secretes trefoil factors that can lead to regeneration of epithelial layer?

Answer 38

Surface mucous cells!

Question 39

What does Gastroferrin do?

Answer 39

Aids in Ferrous (Fe++) iron absorption

Question 40

Where are chief cells?

Answer 40

In the body by the parietal cells

Question 41

What is secreted when there is increased H+ ions, fats, and peptides in the duodenum? What does this do to parietal HCl secretion?

Answer 41

Enterogastrones are secreted (CCK, secretin etc.) They inhibit ECL cell release of Histamine so the Histamine can't bind parietal cells...therefore there is a decrease in acid secretion

Question 42

When is pepsinogen secreted?

Answer 42

In response to ACh and gastrin

Question 43

What inhibits pepsinogen release?

Answer 43

Secretin

Question 44

What is meant by the term "autoactivation" in terms of pepsinogen?

Answer 44

Once pepsinogen hits the acidic environment of the stomach...it is cleaved into pepsin which is a POTENT PROTEOLYTIC ENZYME!

Question 45

Besides pepsinogen, what else do chief cells secrete?

Answer 45

Lipase!

Question 46

Surface epithelial cells secrete mucus and bicarbonate in response to what?

Answer 46

PGE2

Question 47

How do NSAIDs lead to gastric irritation?

Answer 47

They block the production of PGE2...therefore there is reduced mucus secretion...this contributes to gastric irritation

Question 48

How do catecholamines contribute to stress ulcers?

Answer 48

Catecholamines suppress mucosal BICARBONATE secretion...this contributes to gastric irritation and the formation of stress ulcers

Question 49

What are the 4 phases of digestion?

Answer 49

Interdigestive Cephalic Gastric Intestinal

Question 50

If peptic ulcer disease is caused by H pylori, what two things are you going to use to tx?

Answer 50

Antibiotic | PPI

Question 51

How may H pylori contribute to an increase in acid production?

Answer 51

Urease may inhibit somatostatin...this lets Gastrin go wild to act on parietal and ECL cells

Question 52

What 2 ways do NSAIDs contribute to ulcer formation?

Answer 52

No prostaglandins! Normally PGE2 contributes to mucus formation...without it we have less mucus. Without prostaglandins we have tons of histamine release so there is a ton of acid production.

Question 53

What are foveolar cells?

Answer 53

Epithelial cells that secrete mucin.

Question 54

How may H pylori contribute to ulcers?

Answer 54

H pylori has urease which makes the environment more basic. This inhibits somatostatin. We, therefore, have no inhibition of gastrin so a crap ton of gastrin is secreted and we get lots of acid production!