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Case 1 IBD > gastric acid secretion > Flashcards

gastric acid secretion Flashcards

1
Q

2 gland areas of stomach?

A

fundus - acid secreting oxyntic gland area
pylorus - pyloric gland area

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2
Q

cells found in fundus area?

A

mucous cells
chief cells
ECL cells
parietal cells

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3
Q

cells found in pyloric area?

A

mucous cells
G cells
D cells

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4
Q

positive regulators of acid secretion?

A

Acetylcholine (enteric neurons)
histamine (ECL cells)
gastrin (G cells)

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5
Q

negative regulators of acid secretion?

A

somatostatin (D cells)

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6
Q

how does Ach stimulate acid secretion?

A

direct parietal cell stimulation

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7
Q

how does histamine stimulate acid secretion?

A

paracrine activity
direct parietal stimulation

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8
Q

how does gastrin stimulate acid secretion?

A

endocrine action
stimulates histamine release and parietal cell proliferation

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9
Q

how does somatostatin decrease acid secretion?

A

directly inhibits parietal cell secretion
inhibits gastrin and histamine

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10
Q

what are the pathways that induce HCL secretion?

A

Ach and gastrin - PLC IP3 pathway, increased Ca2+
histamine - Increase in cAMP

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11
Q

3 phases that stimulate acid secretion?

A

cephalic phase
gastric phase
intestinal phase

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12
Q

what is the cephalic phase?

A

sight/smell/thought of food increases acid

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13
Q

what is the gastric phase?

A

food in stomach increases pH
prevents D cell activity
peptides in food stimulate G cell activity so gastrin and HCL released

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14
Q

what is the intestinal phase?

A

chyme enters duodenum
feedback prevents chyme acidity
stimulation of hormones
decrease in pH and food stimulates D cell activity

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15
Q

mechanism of HCL secretion?

A
  • CO2 diffuses into parietal cells and is hydrated to carbonic acid
  • acid dissociates into H+ and HCO3-
  • H+/K+ ATPase actively transports H+ out and K+ in
  • Na+ actively reabsorbed
  • K+ recycled to gastric lumen
  • Cl- passively exits
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16
Q

what does the extracellular H+ generate?

A

osmotic gradient across membranes
H2O outward diffusion

17
Q

how is the mucosa protected from HCL?

A

-mucin glycoprotein released due to vagal stimulation and irritation
- gastric surface secretes HCO3- that accumulates near surface and is trapped by mucus

18
Q

why is continual production of mucin required?

A

mucin is cleaved by pepsin

19
Q

why is the mucous layer rich in bicarbonate?

A

creates micro-environment to stop acid damage

20
Q

what do prostaglandins do?

A

reduce HCL secretion
increase mucus and bicarbonate

Case 1 IBD (5 decks)

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