Brainscape's Knowledge GenomeTM

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


See full index

GI > Week 4 - Functions of the stomach > Flashcards

Week 4 - Functions of the stomach Flashcards

1
Q

What prevents a rise in intragastric pressure whilst eating? Explain how this works

A
  • Receptive relaxation ->Vagally mediated relaxation of the orad of the stomach
  • Rugae allow distension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the orad and caudad regions of the stomach?

A
  • Orad is proximal portion consisting of fundus and part of body
  • Caudad is the rest
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What factors allow the stomach to disrupt food? Explain each one

A
  • Peristalsis -> coordinated movements in muscular walls of antrum every 20s from proximal to distal allow mixing of stomach contents to create chyme
  • Shape of stomach-> funnel arrangement causes separation of contents
  • Acidic conditions ->unravels proteins, activates proteases and disinfects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What factor of the stomach aids separation of liquid chime and large contents?

A
  • Shape of stomach -> Larger proximal to smaller distal creates a funnel type arrangement which allows contents to accelerate towards the pyloric sphincter, in such a way that separation of the large contents occurs and the small/liquid chyme is ejected into duodenum
  • Occurs every 3 minutes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Name the importance cells of the stomach and their secretions

A
  • Parietal cells -> HCL and Intrinsic factor
  • Enterochromaffin like cells -> Histamine
  • Chief cells -> pepsinogen
  • G cells -> gastrin
  • D cells -> somatostatin
  • Mucus cells (surface and neck)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are parietal cells mainly located?

A

-Fundus/body

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

Where are G cells mainly located?

A

-Antrum

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

What is the function of histamine in the stomach?

A

-Acts via H2 receptors to mediate acid production

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

What is the function of somatostatin?

A

-Inhibits G cells and ECL cells to decrease acid production

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the function of mucus?

A

-Protect epithelia from the acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the structure of a gastric gland and pit from deep to superficial

A
  • Enteroendocrone cells at the bottom (G and D cells)
  • Chief cells
  • Parietal cells
  • Mucous cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What 3 factors stimulate the parietal cells for HCL production?

A
  • Gastrin (hormone)
  • Histamine (chemical mediator)
  • Ach (neural)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is histamines function of acid production?

A

-Fine tune acid production based on amounts of food entering stomach

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What controls gastrin secretion?

A
  • Presence of peptides and a’a in stomach lumen
  • Vagal stimulation via Ach and gastrin-releasinf peptide
  • Negative control by somatostatin produced by D cells
  • Increasing pH in the stomach due to dilution by food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What inhibits HCl production?

A
  • When food leaves stomach, pH drops and G cells inhibited
  • When food leaves stomach, pH drops and D cells stimulated to inhbit G cells and ECL indirectly
  • Stomach distension reduced-> Vagal activity reduced -> reduced stimulation of G cells and parietal cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the formation of HCl and its byproducts causing alkaline tide

A
  • In the parietal cell, water split into OH and H
  • H moved into stomach lumen
  • Cl moved into stomach lumen (enters parietal cell from ECF in exchange for HCO3)
  • Forms HCl
  • OH combines with CO2 to form HCO3-
  • HCO3 moved into bloodstream forming alkaline tide
17
Q

How is H+ pumped into lumen by parietal cell?

A

-H+/K+ATPase (Proton pump)

18
Q

What are the 3 phases of digestion?

A
  • Cephalic
  • Gastric
  • Intestinal
19
Q

Explain the cephalic phase of digestion

A
  • Prepares stomach for digestion before food enters
  • Produces 30% of total HCl
  • Smelling, tasting, chewing, swallowing stimulates vagal activity
  • Direct stimulation of parietal and G cells
20
Q

Describe the gastric phase of digestion

A
  • Produces 60% of total HCl
  • Distension of stomach stimulates vagus (Parietal and G cells stimulated)
  • Presence of a’a and small peptides stimulates G cells
  • Food acts as a buffer in stomach and increases pH to remove inhibition on gastrin production
21
Q

Describe intestinal phase of digestion

A
  • 10% of HCl production
  • Chyme initially stimulates gastrin
  • Short phase as soon overtaken by inhibition of G cells
22
Q

What are the stomach defences to acid?

A
  • Mucus/HCO3 forms thick alkaline viscous layer which adheres to epithelium -> epithelium kept at higher pH
  • High turnover of epithelia helps to keep epithelia in tact
  • Prostaglandins are vasodilators which help maintain mucousal blood flow supplying the epithelium with nutrients
23
Q

Name 3 common factors which breach stomach defences

A
  • Alcohol dissolves mucous layer
  • H.pylori
  • NSAIDs inhibit PGs
24
Q

Name 2 pharmacologic interventions of acid production

A
  • H2 antagonist (ranitidine)

- Proton Pump Inhibitor (Omeprazole)

25
Q

Why is a PPI better than H2 antagonist?

A
  • H2 antagonist only removes histamine stimulation of parietal cells, Ach and gasrtin still causing production
  • PPI blocks acid production after point of stimulation so all stimulants affected
26
Q

Describe the basic structure of the stomach

A
  • Cardia (where oesophagus joins)
  • Fundus at top
  • Body
  • Antrum at bottom
  • Pylorus and pyloric sphincter
  • Angularis is curve on lesser curvature
  • Has rugue

GI (16 decks)

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