1 Flashcards

1
Q

Outline the functions of the stomach:

A
  • To store and mix food
  • Dissolve and continue digestion
  • Kill microbes
  • Secrete proteases
  • secrete intrinsic factor
  • activate proteases
  • lubrication
  • mucosal protection
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2
Q

What is the purpose of intrinsic factor?

A

It aids absorption of vitamin b12 in the last 12 inches of the ileum.

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3
Q

Outline the anatomy of the stomach:

A

Fundus
Antrum
Pyloris
Pyloric sphincter

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4
Q

What are the 4 main types of cell found in the stomach?

A

Mucous cells
Parietal cells
Chief cells
Enteroendocrine cells

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5
Q

……………… cells sit in adjacent connective tissues beneath the epithelium in the gastric fundus.

A

Enterchromaffin

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6
Q

Enterochromaffin cells secrete ………….

A

Histamine

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7
Q

What is the purpose of gastric acid secretion?

A

To help us to dissolve large chunks of food.

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8
Q

What do parietal cells produce?

A

Gastric acid and intrinsic factor.

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9
Q

The hydrochloric acid in the stomach is very strong at pH ……….

A

2

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10
Q

What is the concentration of H+ in the stomach?

A

[H+] > 150 mM

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11
Q

How much gastric acid is produced per day?

A

approx. 2l/day

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12
Q

Outline the steps in production of gastric acid:

A

IN PARIETAL CELL:

  • H2O breaks down into OH- and H+
  • Co2 + H2O -> H2CO3
  • H2CO3 rapidly dissociates into HC03- and H+
  • H+ produced here react with OH- (from breakdown of water) and regenerate H2O
  • H+ ions from breakdown of H2O pumped into stomach lumen via H+/K+ATPase pump in luminal membrane
  • 1K+ pumped into cell for every 1H+ pumped out ; this ensures there is no change in polarity in the cell
  • K+ pumped into cell diffuse back out via K+ channels in plasma membrane
  • HCO3- from breakdown of H2CO3 is secreted into capillary for exchange of Cl- ions
  • Cl- enter stomach by diffusion through Cl- channels
  • In stomach, H+ and Cl- react to form HCl
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13
Q

What enhances the forward rate of reaction?

A

The removal of the end product. The production and secretion of H+ are coupled.

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