Gastric Secretions

Question 1

What is the enzyme that H pylori bacteria secrete that allow them to survive in the acidic environment of the stomach? What is the toxin they secrete?

Answer 1

Urease

Cytoxin = VacA

Question 2

What are the cell types in the gastric pits?

Answer 2

Parietal cell

Chief cells

Question 3

What do chief cells produce?

Answer 3

Pepsinogen

Question 4

What do parietal cells secrete? Function?

Answer 4

HCl

Protein digestion, sterilization, nutrient absorption

Question 5

What cells secrete intrinsic factor? Function?

Answer 5

Parietal cells

Vit B12 absorption

Question 6

What cells secrete pepsinogen? Function?

Answer 6

Chief cells

Protein digestion

Question 7

What cells secrete mucus and bicarb in the stomach?

Answer 7

Superficial epithelial cells

Question 8

What cells produce histamine in the stomach? Function?

Answer 8

ECL cells

Promotes HCl production

Question 9

What cells produce gastrin? Function?

Answer 9

G cells

Promotes HCl secretion

Question 10

What cells produce Ach in the stomach? Function?

Answer 10

Nerve cells

Promotes mucus, bicarb, and HCl secretion

Question 11

What cells produce somatostatin in the stomach? Function?

Answer 11

D cell

Suppresses HCl secretion

Question 12

Are there any parietal cells in the cardia portion of the stomach? What is the function of this?

Answer 12

No, protects esophagus

Question 13

What are the four cell types in the body of the stomach?

Answer 13

1. Parietal cells
2. Chief cells
3. Neck cells
4. Enterochromaffin cells (ECL)

Question 14

What are the three cell types in the antrum of the stomach?

Answer 14

1. Chief cells
2. G cells
3. D cells

Question 15

What are the two fundamental types of secretion in the stomach? What cells produce each? What happens with increased stimulation of the stomach to the activity of each?

Answer 15

Na rich secretion from non-parietal cells–these decrease with increased stimulation of the stomach

H rich from parietal cells–these increase with stimulation of the stomach

Question 16

What is the pump and enzyme utilized to make HCl?

Answer 16

H-K ATPase (proton pump)

Carbonic anhydrase

Question 17

How large is the vesicular supply of proton pumps (relatively)?

Answer 17

Super large

Question 18

What are the three pathways that acid secretion is stimulated through? Transmitter for each?

Answer 18

Paracrine (histamine)
Endocrine (gastrin)
Neuronal (Ach)

Question 19

What is the effect of the low pH on bile and pancreatic enzyme flow?

Answer 19

increases

Question 20

What are the receptors on the parietal cells for that regulate acid secretion?

Answer 20

Muscarinic (Ach)
H2 receptor (G protein)
Gastrin receptor

Question 21

What are the two indirect pathways that acid secretion is regulated through?

Answer 21

Endocrine (gastrin, somatostatin)

Neuronal (Ach)

Question 22

What are the cells that sense amino acids in the stomach? What does this cell type secrete? What does this cause?

Answer 22

G cells
Gastrin
Increases HCl secretion

Question 23

What are the cells that sense low pH in the stomach? What does this cell secrete?

Answer 23

D cell

Somatostatin to reduce acid secretion

Question 24

What is the protein that binds B12 in the intestine?

Answer 24

Intrinsic factor

Question 25

Damage to the parietal cells will cause what two things?

Answer 25

Lower Vit B12 absorption Increased pH of the stomach

Question 26

What are the primary cells that secrete pepsinogen? What is the key neurotransmitter that stimulates pepsinogen release?

Answer 26

Chief cells Ach (but others as well)

Question 27

What cleaves pepsinogen to pepsin? How does the activity of pepsinogen change in response to lower/higher pHs?

Answer 27

HCl Lower pH generally better and v.v.

Question 28

What is the function of pepsin?

Answer 28

Destroys proteins (protease)

Question 29

What are the protective factors against HCl and pepsin? (2)

Answer 29

Mucus (Mucin, phospholipids, electrolytes, water) Bicarb

Question 30

What is the pH near the epithelial cell layer of the stomach? How?

Answer 30

High d/t bicarb and mucus secretions

Question 31

What is the neurocrine regulator of protective factor secretion? Paracrine? What does each do?

Answer 31

``` Neurocrine = Ach (promotes mucus and bicarb secretion) Paracrine = prostaglandins (ditto above, and suppress acid secretion) ```

Question 32

What are the roles of prostaglandins in the stomach?

Answer 32

1. Mucus and bicarb secretion 2. Suppression of HCl secretion 3. Increased gastric flow

Question 33

What is gastritis?

Answer 33

Inflammation of the gastric lining

Question 34

What is the MOA of increased number of parietal cells causing acid-peptic disease?

Answer 34

Increase HCl secretion

Question 35

What is the MOA of high serum gastrin levels causing acid-peptic disease?

Answer 35

Increases acid secretion

Question 36

What is the MOA of a loss of acid-mediated negative feedback on gastrin secretion causing acid-peptic disease?

Answer 36

Increases acid secretion

Question 37

What is the MOA of Rapid gastric empyting causing acid-peptic disease?

Answer 37

Too fast = not enough time to buffer

Question 38

What is the MOA of H.Pylori infx causing acid-peptic disease?

Answer 38

Releases toxin and immune response

Question 39

What is the MOA of NSAID use causing acid-peptic disease?

Answer 39

Inhibits PGE2, causing H2 receptor to be uninhibited

Question 40

What are the degradation products of urea?

Answer 40

Bicarb | Ammonium ion

Question 41

What causes the damage seen in H.pylori infx?

Answer 41

Inflammatory response to the H.Pylori colonization

Question 42

What is the enzyme that NSAIDs inhibit that reduce prostaglandin synthesis?

Answer 42

COX1/2

Question 43

What is the MOA of H2 inhibitors?

Answer 43

Blocks histamine, thereby decreasing HCl secretion

Question 44

What is the MOA of pepto bismol (bismuth salts)?

Answer 44

Substitute for the mucus

Question 45

Where do the Histamine and PGE2 receptors on the parietal cell converge? What is the consequence of this?

Answer 45

On the G protein receptors Have opposite effects (PGE2 inhibits)

Question 46

What are the histamine producing cells of the stomach? What neurotransmitters do these respond to?

Answer 46

ECL cells Respond to ACh, and gastrin

Question 47

Gastrin and ACh have both indirect and direct effects on HCl release. How?

Answer 47

Direct = receptors on parietal cells Indirect = receptors on ECL cells that produce histamine (which also increases HCl production)

Question 48

How do the gastric pits secrete acid to ensure that not all of the H+ ions secreted are buffered by the mucus/bicarb layer?

Answer 48

Contractile squirting into the lumen of the stomach

Question 49

What are the three key roles of PGE2 production?

Answer 49

1. Mucus and bicarb secretion 2. Suppression of HCl 3. Increased gastric blood flow

Question 50

Why are PPIs chosen over H2 receptor antagonists?

Answer 50

Because PPIs regulate at the common pathway for all three ACh, H2, and Gastrin, thus hit three acid secreting receptors instead of just one

Question 51

What is the secretion that non-parietal cells secrete at a basal level? What happens to this as the secretory rate of the stomach increases?

Answer 51

Na-rich secretion, which decreases with increased stimulation of the stomach

Question 52

What are the four phases of acid secretions?

Answer 52

1. Interdigestive phase 2. Cephalic phase 3. Gastric phase 4. Intestinal phase

Question 53

What is the interdigestive phase of gastric acid secretion?

Answer 53

Between digesting times, low acid secretion

Question 54

What is the cephalic phase of gastric acid secretion?

Answer 54

This phase is activated by stimuli such as the sight or smell of food, which increases gastric acid secretion

Question 55

What is the gastric phase of acid secretion?

Answer 55

Vagal stimulation to increase acid in response to distension/protein products of the stomach

Question 56

What are the cells in the stomach that ensure that pH does not get too low? What chemical do they produce, and what is its effect?

Answer 56

D cells, which will secrete somatostatin to reduce gastric secretion

Question 57

What is the intestinal phase of acid secretion?

Answer 57

Presence of peptides in the duodenum increases acid secretion via the release of gastrin from G cells

Question 58

What cells in the duodenum sense the presence of protein? What do they secrete?

Answer 58

G cells-- gastrin to increase the rate of acid secretion.

Question 59

What cells produce IF?

Answer 59

Parietal cells

Question 60

What cells produce the mucus lining of the stomach? Where in the stomach are these found?

Answer 60

Epithelial cells--everywhere

Question 61

What are the two key neurotransmitters that stimulate epithelial and neck cells to produce mucus and HCO3 in the stomach?

Answer 61

ACh and Prostaglandins

Question 62

A break in the protective mucosal lining of the lower esophagus, stomach, or duodenum = ?

Answer 62

Peptic ulcer

Question 63

What ulcer occurs with the greatest frequency?

Answer 63

Duodenal ulcers

Question 64

Peptic ulcer caused by illness, systemic trauma, neuronal injury, emotions = ?

Answer 64

Stress ulcer

Question 65

What is a stress ulcer associated with head trauma or brain surgery?

Answer 65

Cushing ulcer

Question 66

What are ulcers caused by hemorrhage, multi-system trauma, severe burns, heart failure, or sepsis?

Answer 66

Ischemic ulcers

Question 67

What is Zollinger-Ellison syndrome?

Answer 67

gastrin-secreting tumor of the pancreas that stimulates the acid-secreting cells of the stomach (parietal cells) to maximal activity, with consequent gastrointestinal mucosal ulceration. ZES may occur sporadically or as part of an autosomal dominant familial syndrome called multiple endocrine neoplasia type 1 (MEN 1)