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yr2 > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

Fundus

A

(top part)

Storage

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2
Q

Body

A

(middle)

Storage, HCL, mucus, pepsinogen, intrinsic factor

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3
Q

Antrum

A

(bottom)
Mixing & grinding food
Gastrin (hormone for HCL release by g cells)

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4
Q

3 Gastric gland cells:

A
  1. Mucous neck cells (mucous)
  2. Chief cells (pepsinogen)
  3. Parietal cells (HCL & intrinsic factor)
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5
Q

Pepsin is stored in an inactive form as pepsinogen to prevent

A

degradation of proteins in stomach wall

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6
Q

CO2 waste product in blood enters stomach cell, combines with H2O to give

A

carbonic acid, which dissociates into bicarbonate & hydrogen ions

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7
Q

H ion then actively transported into stomach lumen using

A

hydrogen potassium ATPase (Stomach lumen pH<2)

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8
Q

Bicarbonate (HCO3) ion is released back into blood in exchange for

A

CL in (blood pH>7.4)

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9
Q

CL diffuses into

A

stomach lumen

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10
Q

Stomach lumen pH:

A

pH<2

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11
Q

3 types of control of gastric acid secretion:

A
  1. Neurocrine (vagus/local reflexes)
  2. Endocrine (gastrin)
  3. Paracrine (histamine)
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12
Q

3 types of control of gastric acid secretion:

A
  1. Neurocrine (vagus/local reflexes)
  2. Endocrine (gastrin)
  3. Paracrine (histamine)
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13
Q

Cephalic phase stimulation (in head):

A
  1. Sight, smell, taste
  2. Increase vagus nerve activity
  3. Ach release, gastrin release by G cells (increase HCL release by parietal cells)
  4. Release of ach and gastrin also stimulate enterochromaffin-like cells to release histamine (increase HCL release by parietal cells)
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14
Q

Gastric phase stimulation:

A
  • Stomach stretching -> stimulate vagus/enteric reflex -> Ach released
  • Peptide in lumen -> stimulate G cells -> gastrin released
  • Gastrin/Ach release -> enterochromaffin-like cells -> histamine released
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15
Q

Mechanisms Stimulating

Gastric Acid Secretion involves:

A

Cephalic phase & Gastric phase

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16
Q

Mechanisms Inhibiting

Gastric Acid Secretion involves:

A

Cephalic phase, Gastric phase, Intestinal phase

17
Q

For gastric acid secretion inhibition, in the Cephalic phase what happens?

A

stop eating –> vagal activity reduced

18
Q

For gastric acid secretion inhibition, in the Gastric phase what happens?

A

decrease in pH by overproduction of HCL that is not used –> reduced gastrin release

19
Q

Intestinal phase

A
  • Acid in duodenum from stomach activates enterogastric reflex & released secretin
  • This reduces gastrin stimulation & release)
  • When fat and carbs enter duodenum, gastric inhibitory peptide released, gastrin & HCL secretion reduced
20
Q

What are Enterogastrones?

A

Hormones released from gland cells in duodenal mucosa - secretin, cholecystokinin (CCK), GIP

21
Q

When are Enterogastrones released?

A
  • Released in response to acid, hypertonic solutions, fatty acids or monoglycerides in duodenum
  • Act collectively to prevent further acid build up in duodenum
22
Q

Enterogastrones have 2 strategies:

A
  1. Inhibit gastric acid secretion

2. Contract pyloric sphincter to prevent acid moving down

23
Q

What is Pepsinogen?

A

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

24
Q

Pepsinogen is stored as an

A

inactive precursor (secreted by Chief cells)

25
Q

Pepsins inactivated at what pH?

A

neutral pH (to prevent cellular damage)

26
Q

Pepsinogen cleaved into pepsin at what pH?

A

pH<3 (low pH)

27
Q

Inactive precursor =

A

Zymogen

28
Q

What is gastric mucus produced by?

A

surface epithelial cells & mucus beck cells

29
Q

What does gastric mucus do?

A
  • Protects mucosal surface from mechanical injury

- Protects against gastric acid corrosion & pepsin digestion

30
Q

Intrinsic factor produced by

A

Parietal cells

31
Q

Intrinsic factor required for

A

vitamin B12 absorption

32
Q

Intrinsic factor/B12 complex absorbed from

A

ileum

33
Q

Defect in intrinsic factor causes

A

Pernicious Anaemia (failure of erythrocyte maturation)

yr2 (9 decks)

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