Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Digestive System > Secretions of the Stomach > Flashcards

Secretions of the Stomach Flashcards

1
Q

What are the functions of the stomach

A
  • Stores food
  • Mixes food with secretions
  • Regulates release of food into duodenum
  • Secretes gastric juices
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Anatomy

A

of stomach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What substances do mucous neck cells secrete

A
  • Mucous
  • Bicarbonate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What substances do parietal cells secrete

A
  • Acid
  • IF (intrinsic factor)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What substances do EC like cells secrete

A
  • Histamine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What substances do chief cells secrete

A
  • Pepsinogen
  • Lipase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What substances do D cells secrete

A
  • Somatostatin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What substances do G cells secrete

A
  • Gastrin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where in the stomach are a majority of parietal cells found

A
  • The corpus (or body) of the stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where in the stomach are a majority of G cells found

A
  • The antrum of the stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where in the stomach are a majority of D cells found

A
  • They are distributed across the stomach
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What mediates the acid secretion in parietal cell and where is this located

A
  • H+/K+ pump that requires energy in the form of ATP
  • It is located in the apical membrane of the parietal cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What 2 types of subunits does the H-K pump require for full activity and state a reason for requiring each subunit

A
  • Alpha subunit for catalytic function
  • Beta subunit for apical membrane targeting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the action of the H-K pump and why does this occurs

A
  • Action - Extrudes H+ into the lumen of the gastric gland
  • Why - The H+ is exchanged for a K+ ion which is recycled in the lumen via K+ channels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the original H+ ion that is forced into the lumen of the gastric gland generated generated

A
  • Generated from carbonic acid using carbonic anhydrase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens to the H+ ion that is forced into the lumen of the gastric gland

A
  • It combines with Cl- that has left cells through ion channels to produce HCl
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Give the carbonic anhydrase catalysed reaction

A

H20+CO2->H2CO3->HCO3-+H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens to the HCO3- produced when generating H+

A

It exists the basolateral membrane via the Cl-, HCO3- exchanger then enters the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the movement of HC03- ions into the blood called

A
  • Alkaline tide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the 2 types of regulation of acid secretion by parietal cells

A
  • Direct Regulation - Action triggers proton efflux via H+/ K+ pumps
  • Indirect regulation - Releasing another substance (histamine) that stimulates acid production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the 3 stimuli that directly regulate acid production

A
  • Ach
  • Histamine
  • Gastrin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How does Ach directly regulate acid production

A
  • Eating a meal causes stretching in the stomach which stimulates the vagus nerve releasing Ach as the neurotransmitter.
  • Ach binds to M3 receptor which stimulates acid production in parietal cells4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does histamine directly regulate acid production

A

-Produced by ECL cells
-Binds to H2 receptor on parietal cells and triggers acid production.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does gastrin directly regulate acid production

A
  • Produced by G cells.
  • Binds to Gastrin receptor on parietal cells and stimulates acid production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How does indirect regulation of acid production occur via histamine

A
  • Ach and gastrin stimulate ECL cells to produce histamine
  • Histamine stimulates acid production in parietal cells.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Out of Ach, histamine and gastrin which has the most impact on regulating acid production and why

A
  • Histamine
  • Has both direct and indirect effects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What pathway stimulates H+/K+ pumps when histamine binds to a H2 receptor

A
  • An adenyl cyclase-camp-PKA pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What pathway stimulates H+/K+ pumps when gastrin or Ach bind to their respective receptors.

A
  • PLC/PKC/Ca2+ pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the name of the major inhibitor for acid production

A
  • Somatostatin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How does somatostatin inhibit acid production

A
  • It antagonises the adenyl cyclase pathway (inhibiting the action of histamine)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What inhibits somatostatin production

A
  • Vagus nerve stimulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens in the corpus of the stomach

A
  • Ach is released from the vagus nerve due to distension of stomach
33
Q

What effects does Ach have in the stomach

A
  • Direct stimulation of parietal cells to induce acid release.
  • indirect stimulation of parietal cells by causing E cells to release histamine.
  • Stimulates D cell which inhibits the release of somatostatin.
34
Q

What 2 types of cells are stimulated in the antrum by vagal stimulation

A
  • G cells - via GRP
  • D cells - via Ach
35
Q

What stimulates D cells to release somatostatin (not vagal nerve stimulation)

A
  • Products of protein digestion such as peptides and amino acids
36
Q

What stimulates G cells to release somatostatin (not vagal nerve stimulation)

A
  • High luminal H+
37
Q

What is secretin and how does it work

A
  • Inhibitor of acid secretion
  • Works by inhibiting the release of gastrin in the antrum and releasing somatostatin
38
Q

What releases secretin

A
  • Duodenal S cells
39
Q

What stimulates secretin production

A
  • Fat and acid in duodenum
40
Q

What is CCK and how does it work

A
  • Inhibitor of acid production
  • Works by directly decreasing parietal-cell acid secretion
41
Q

What releases CCK

A
  • I cells in Duodenum and jejunum
42
Q

What stimulates CCK production

A
  • Fat
43
Q

Give examples of pharmacological inhibitors of acid secretion

A
  • Proton pump inhibitors
  • H2 receptive antagonist
44
Q

How do H2 receptor antagonist work

A
  • Competitive antagonist of histamine at parietal cell H2 receptor.
45
Q

Which pharmacological inhibitor of acid secretion is the best and why

A
  • PPI
  • RA’s only supress acid production via histamine, however histamine is still a large proportion of acid production stimulation so RAs are still used
46
Q

What are the 4 phases of gastric acid secretion

A

1) Basal Phase
2) Cephalic (30%)
3) Gastric (50%-60%)
4) Intestinal (5%-10%)

47
Q

What type of rhythm does the basal phase follow

A
  • Circadian rhythm - Low acid production in a.m high acid production in p.m
  • No. of parietal cells determines acid production (size of stomach)
48
Q

What can trigger the cephalic phase

A
  • Smell
  • Sight
  • Taste
  • Thought
  • Swallowing
49
Q

What stimulates acid production in the gastric phase

A
  • Distension of the stomach by food
50
Q

What stimulates acid production in the intestinal phase

A
  • Partially digested peptides and amino acids
51
Q

What are Pepsinogens

A
  • Proteolytic proenzymes secreted by chief cells
52
Q

What is a major trigger for pepsinogen secretion

A
  • Ach
53
Q

How does pepsinogen become is active form (pepsin)

A
  • Conversion happens spontaneously at pH <5
54
Q

What effect does pepsin have on pepsinogen

A
  • Cascade effect - Pepsin autoactivates pepsinogen
55
Q

When does pepsin become irreversibly inactivated

A
  • pH of 7.2
  • In the small intestines
56
Q

What is an endopeptidase

A
  • Protease
  • A protease enzyme that initiates protein digestion by cleaving amino acids anywhere but their terminal ends.
57
Q

What is the link between acid secretion and pepsinogen activity

A
  • Smaller peptides and amino acids cleaved by pepsinogen trigger G cell gastrin secretion the antrum
58
Q

Why is gastric mucosal protection needed

A
  • The contents of stomach lumen create a harsh environment
59
Q

How is the lining of the stomach protected

A
  • Mucousal layer traps HCO3- which maintains a pH of around 7
60
Q

How do prostaglandins maintain the mucosal diffusion barrier

A
  • Inhibit acid secretion stimulating HCO3- and mucus secretion
61
Q

Give an example that proves the importance of prostaglandins

A
  • Effects of non selective NSAIDS on gastric mucosa
62
Q

What makes prostaglandins

A
  • A precursor called arachidonic acid
63
Q

What 2 types of prostaglandins does arachidonic acid produce

A
  • Prostaglandins involved in pathology (inflammation)
  • Prostaglandins involved in physiology
64
Q

What enzyme is responsible for the production of prostaglandins that are involved in inflammation and what is important about this enzyme

A
  • Cyclooxygenase - 2 (COX 2)
  • It is inducible - not switched on all the time
65
Q

What enzyme is responsible for the production of prostaglandins that are involved in physiology and what is important about this enzyme

A
  • Cyclooxygenase - 1 (COX 1)
  • Constitutively active - always there
66
Q

What issue does inhibiting the effect of arachidonic acid have when taking NSAIDs

A
  • COX -1 and COX - 1 are both inhibited
  • This means that the prostaglandins involved in gastric mucosal protection are not produced either.
67
Q

What are some common side effects of using non selective NSAIDs to treat inflamation

A
  • Gastric ulceration
  • Dyspepsia
68
Q

Give an example of a selective COX-2 inhibitor and why it has been withdrawn

A
  • Vioxx
  • Increases risk of heart attack
69
Q

What is Helicobacter Pylori (H. Pylori) and what is it classified as

A
  • Gram-negative microaerophilic bacterium
  • Classified as a carcinogen.
70
Q

What percentage of human stomachs are colonised by H. Pylori

A
  • 40%
71
Q

What can H. Pylori cause

A
  • Gastritis
  • Peptic, gastric and duodenal ulcers
  • Gastric cancer
72
Q

How does H. Pylori cause stomach ulcers

A
  • Flagellum moves H. Pylori to stomach/duodenum
  • Produces mucinase to breakdown mucin to weaken mucosal coating
  • H. Pylori binds to gastric mucosal cells via lipopolysaccharides
  • Also allows acid to reach mucosa causing peptic ulcer
73
Q

How does H. Pylori survive the pH of stomach acid

A
  • Synthesises urease enzyme which breaks down urea into an ammonium ion and a bicarbonate ion.
  • The bicarbonate ion neutralises stomach acid
74
Q

How does H. Pyloris infection in the antrum cause hypergastrinemia and ultimately duodenal ulcers

A
  • Causes G cells to hyper secrete gastrin leading to lots of acid being produced
  • Decreases antral D-cell somatostatin production
75
Q

What does H. Pyloris infection in the corpus cause

A
  • Reduced acid secretion
  • Hypochlorhydria (highly associated with gastric ulcers)
76
Q

What is triple therapy

A
  • Treatment using 2 antibiotics (amoxicillin and clarithromycin) and a proton pump inhibitor
77
Q

What is intrinsic factor produced by and why is it necessary

A
  • Produced by parietal cells
  • Necessary for Vitamin B12 production in the terminal ileum
78
Q

What is the effect of a lack of Vitamin B12

A

Addison’s Anaemia/ Percinicous anaemia

79
Q

What is Addison’s Anaemia/ Percinicous anaemia and what does it cause

A
  • Autoimmune atrophic gastritis, autoantibodies destroy parietal cells
  • Can cause megaloblastic anaemia

Digestive System (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions