Gastric Secretions Flashcards Preview

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Flashcards in Gastric Secretions Deck (67):
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?

Urease

Cytoxin = VacA

2

What are the cell types in the gastric pits?

Parietal cell
Chief cells

3

What do chief cells produce?

Pepsinogen

4

What do parietal cells secrete? Function?

HCl

Protein digestion, sterilization, nutrient absorption

5

What cells secrete intrinsic factor? Function?

Parietal cells

Vit B12 absorption

6

What cells secrete pepsinogen? Function?

Chief cells

Protein digestion

7

What cells secrete mucus and bicarb in the stomach?

Superficial epithelial cells

8

What cells produce histamine in the stomach? Function?

ECL cells

Promotes HCl production

9

What cells produce gastrin? Function?

G cells

Promotes HCl secretion

10

What cells produce Ach in the stomach? Function?

Nerve cells

Promotes mucus, bicarb, and HCl secretion

11

What cells produce somatostatin in the stomach? Function?

D cell

Suppresses HCl secretion

12

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

No, protects esophagus

13

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

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

14

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

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

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?

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

16

What is the pump and enzyme utilized to make HCl?

H-K ATPase (proton pump)

Carbonic anhydrase

17

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

Super large

18

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

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

19

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

increases

20

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

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

21

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

Endocrine (gastrin, somatostatin)
Neuronal (Ach)

22

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

G cells
Gastrin
Increases HCl secretion

23

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

D cell

Somatostatin to reduce acid secretion

24

What is the protein that binds B12 in the intestine?

Intrinsic factor

25

Damage to the parietal cells will cause what two things?

Lower Vit B12 absorption

Increased pH of the stomach

26

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

Chief cells

Ach (but others as well)

27

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

HCl

Lower pH generally better and v.v.

28

What is the function of pepsin?

Destroys proteins (protease)

29

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

Mucus (Mucin, phospholipids, electrolytes, water)

Bicarb

30

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

High d/t bicarb and mucus secretions

31

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

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

32

What are the roles of prostaglandins in the stomach?

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

33

What is gastritis?

Inflammation of the gastric lining

34

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

Increase HCl secretion

35

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

Increases acid secretion

36

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

Increases acid secretion

37

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

Too fast = not enough time to buffer

38

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

Releases toxin and immune response

39

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

Inhibits PGE2, causing H2 receptor to be uninhibited

40

What are the degradation products of urea?

Bicarb
Ammonium ion

41

What causes the damage seen in H.pylori infx?

Inflammatory response to the H.Pylori colonization

42

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

COX1/2

43

What is the MOA of H2 inhibitors?

Blocks histamine, thereby decreasing HCl secretion

44

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

Substitute for the mucus

45

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

On the G protein receptors

Have opposite effects (PGE2 inhibits)

46

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

ECL cells

Respond to ACh, and gastrin

47

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

Direct = receptors on parietal cells

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

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?

Contractile squirting into the lumen of the stomach

49

What are the three key roles of PGE2 production?

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

50

Why are PPIs chosen over H2 receptor antagonists?

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

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?

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

52

What are the four phases of acid secretions?

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

53

What is the interdigestive phase of gastric acid secretion?

Between digesting times, low acid secretion

54

What is the cephalic phase of gastric acid secretion?

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

55

What is the gastric phase of acid secretion?

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

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?

D cells, which will secrete somatostatin to reduce gastric secretion

57

What is the intestinal phase of acid secretion?

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

58

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

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

59

What cells produce IF?

Parietal cells

60

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

Epithelial cells--everywhere

61

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

ACh and Prostaglandins

62

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

Peptic ulcer

63

What ulcer occurs with the greatest frequency?

Duodenal ulcers

64

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

Stress ulcer

65

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

Cushing ulcer

66

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

Ischemic ulcers

67

What is Zollinger-Ellison syndrome?

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)