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Alimentary System > Gastric secretion > Flashcards

Gastric secretion Flashcards

1
Q

What is the main function of the fundus of the stomach?

A

Storage

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2
Q

What are the functions of the body of the stomach?

A

Storage

Mucus

GCL

Pepsinogen

Intrinsic factor

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3
Q

What are the functions of the antrum of the stomach?

A

Mixing/grinding

Gastrin

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4
Q

What do mucous neck cells of gastric glands secrete?

A

Mucus

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5
Q

What do chief cells of gastric glands secrete?

A

Pepsinogens

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6
Q

What do parietal cells of gastric glands secrete?

A

HCl (hydrochloric acid)

Intrinsic factor

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7
Q

What does hydrochloric acid (HCL) do in the stomach?

A

Hydrochloric acid activates pepsinogen into the enzyme pepsin, which then helps digestion by breaking the bonds linking amino acids

  • This is known as proteolysis.
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8
Q

What pH is the stomach lumen?

A

pH < 2

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9
Q

What is the normal pH of blood?

A

Around 7.4

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10
Q

What 3 mechanisms is gastric acid secretion controlled by?

A

Neurocrine (vagus/local reflexes)

Endocrine (gastrin)

Paracrine (histamine)

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11
Q

What are different mechanisms stimulating gastric acid secretion (Cephalic phase)?

A

Sight, smell, taste of food > increased vagus nerve activity > +acetylcholine > Parietal cells

Sight, smell, taste of food > Increased vagus nerve activity > G cells > +Gastrin > Parietal cells

Gastrin/ACh > ECL cells > +Histamine > Parietal cells

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12
Q

What are the different mechanisms of the gastric phase?

A

Distension of stomach (arrival of food) > Vagal/enteric reflexes > +ACh > Parietal cells

Peptides in lumen > G cells > +Gastrin > Parietal cells

Gastrin/ACh > ECL cells > +Histamine > Parietal cells

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13
Q

What is a mechanism inhibiting gastric acid secretion during the Cephalic phase?

A

Stopping eating > Decreased vagal activity

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14
Q

What is a mechanism inhibiting gastric acid secretion during the Gastric phase?

A

Decreased pH (increased HCl) > Decreased gastrin

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15
Q

What are mechanisms inhibiting gastric acid secretion during the intestinal phase?

A

Acid in duodenum > enterogastric (splanchnic) reflex > decreased gastrin stimulation of parietal cells

Fat/CHO in duodenum > GIP release > decreased gastrin secretion > decreased parietal HCl secretion

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16
Q

What are enterogastrones?

A

Hormones released from gland cells in duodenal mucosa

  • Secretin, cholecystokinin (CCK), GIP
17
Q

When are enterogastrones released?

A

Released in response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum

  • They act collectively to prevent further acid build up in duodenum
18
Q

What are the 2 strategies enterogastrones use to prevent further acid build up in duodenum?

A
  1. Inhibit gastric acid secretion

2. Reduce gastric emptying (inhibit motility/contract pyloric sphincter)

19
Q

What is pepsinogen?

A

A substance which is secreted by the stomach wall and converted into the enzyme pepsin by gastric acid

20
Q

What cells secrete pepsinogen/

A

Chief cells

21
Q

When is pepsin activated?

A

Low pH < 3

Pepsinogen > Pepsin

22
Q

What happens to pepsins at neutral pH?

A

It is inactivated

23
Q

What is gastric mucus produced by?

A

It is produced by surface epithelial cells and mucus neck cells

24
Q

What is the role of gastric mucus?

A

Protects mucosal surface from mechanical injury

Neutral pH (HCO3) > protects against gastric acid corrosion and pepsin digestion

25
Q

What is an Intrinsic factor?

A

Required for vitamin B12 absorption

  • Only essential (non-compensated) function of stomach
26
Q

What are intrinsic factors produced by?

A

Parietal cells

27
Q

What does intrinsic factor defect cause?

A

Pernicious anaemia (failure of erythrocyte maturation)

Alimentary System (8 decks)

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