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MBChB - Y2 - Systems - Gastrointestinal > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

What does the body of the stomach produce?

A

Mucus

HCL

Pepsinogen

Intrinsic factor

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2
Q

What is the antrum responsible for?

A

Mixing/grinding

Gastrin produciton

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3
Q

Describe the wall of the fundus

A

Thin and stretchy

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4
Q

What are the three main parts of the gastric glands?

A

Mucous neck cells

Parietal cells

Chief cells

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5
Q

What do mucous cells secrete?

A

Mucus

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6
Q

What do parietal cells produce?

A

HCL

Intrinsic factor

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7
Q

What do chief cells produce

A

Pepsinogens

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8
Q

How are hydrogen ions expelled from gastric cells?

A

CO2 enters the cell and combines with water to form carbonic acid - this dossocaites to form carbonate and Hydrogen ion.

Carbonate leaves the cell by chloride shift

Hydrogen leaves the cell by a potassium coupled carrier (1 hydrogen out, 1 potassium in)

H20 moves as a result of the high osmolarity in the stomach lumen

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9
Q

Where is gastrin secreted and where is the receptor?

A

Gastrin secreted from the antrum, receptor is on the basolateral membrane of the body of the stomach - results in increased activity of the hydrogen - potassium carrier

Gastrin increases intracellular calcium (activating protein kinase C)

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10
Q

Which other compunds result in an increased activity of the potassium hydrogen carrier?

A

Histamine and acetycholine

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11
Q

What is the effect of prostaglandins?

A

Activate the inhibatory G protein, which results in inhibition of the hydrogen - potassium carrier

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12
Q

What are the three mechanisms that control gastric secretion?

A

Neurocrine (Vagus/local reflexes)

Endocrine (gastrin)

Paracrine (histamine)

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13
Q

How are paracrine hormones spread?

A

Interstitial pathway

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14
Q

What is the result of the sight, smell and taste of food on vagal tone?

A

Vagal tone increases

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15
Q

What is the result of increased vagal tone on acetylcholine and gastrin?

A

Increases acetylcholine production and causes an increase in Gastrin produciton by G cells

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16
Q

How do ECL (enterochromaffin like cells) respond to the increase in Gastrin and Acetycholine?

A

Release histamine

17
Q

Which cells do acetycholine, gastrin and histamine act on?

A

Parietal cells

18
Q

How is the vagal/ enteric reflex activated in the gastric phase?

A

Distension of stomach and arrival of food

19
Q

What activates the g cells and causes the resultant increase in gastrin in the gastric phase?

A

Peptides in lumen

20
Q

In the gastric phase what causes the ECL cells to release histamine?

A

Gastrin/ACh

21
Q

What inhibits gastric secretion in the cephalic phase?

A

Stopping eating - reduces vagal activity

22
Q

How is gastric acid secretion reduced in the gastric phase?

A

A falling pH reduces Gastrin production

23
Q

What is the effect of acid in the duodenum in the intestinal phase?

A

Activates the enterogastric reflex

Secretin is released - reduces the secretion of gastrin and reduces the effectiveness of gastrin on the parietal cells

(Secretin also makes the pancreas and liver produce bicarbonate)

24
Q

What is the result of fat in the duodenum in the intestinal phase?

A

GIP release - reduces gastrin secretion - resultant decrease on HCL production by the parietal cells

25
Q

Summary of inhibition of gastric acid secretion

A
26
Q

What are enterogastrones?

A

Hormones released from gland cells in the duodenal mucosa

27
Q

Give exmamples of enterogastrones

A

•secretin, cholecystokinin (CCK), GIP (gastro inhibitory peptide)

28
Q

When are enterogastrones released?

A

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

29
Q

What is the effect of enterogastrones?

A
  • Act collectively to prevent further acid build up in duodenum
  • Two strategies:
  • inhibit gastric acid secretion
  • reduce gastric emptying (inhibit motility/contract pyloric sphincter)
30
Q

Define zymogen

A

Inactive precursor

•Zymogen storage prevents cellular digestion

31
Q

What inactivates pepsins?

A

Neutral pH

Pepsin is liberated by low pH – acid hydrolysis

32
Q

What is the control mechanism for pepsinogen release?

A

Mirrors the release mechanism of HCL

(released in response to ACh, Gastrin, Histamine)

33
Q

What produces gastric mucus?

A

surface epithelial cells and mucus neck cells

34
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
35
Q

What produces intrinsic factor?

A

Parietal cells

36
Q

What is intrinsic factor essential for?

A

Vitamin B12 absorption

37
Q

Where is the intrinsic factor/vitamin B12 complex absorbed from?

A

The ileum

•Defect ® Pernicious Anaemia (failure of erythrocyte maturation)

38
Q
A

MBChB - Y2 - Systems - Gastrointestinal (38 decks)

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