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GI and metabolism > The stomach > Flashcards

The stomach Flashcards

1
Q

What are the functions of the stomach?

A

Ingestion Mechanical processing Digestion Secretion Absorption Excretion

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2
Q

Name some notable compounds absorbed in the stomach.

A

Alcohol

NSAIDS

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3
Q

Describe the muscular layers of the stomach, starting with the most luminal.

A

Oblique layer overlying mucosa Circular layer Longitudinal layer

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4
Q

Describe the secretions and functional motility of the cardia (and lower oesophageal sphincter).

A

Mucous, HCO3-

Prevention of reflux, entry of food, regulation of belching.

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5
Q

Describe the secretions and functional motility of the fundus and body.

A

H+, intrinsic factor, mucous, HCO3-, pepsinogens, lipase

Reservoir, tonic force during emptying

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6
Q

Describe the secretions and functional motility of the antrum and pylorus.

A

Mucous, HCO3-

Mixing, grinding, sieving, regulation of emptying

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7
Q

How does accomodation work?

A

Accommodation depends on stretch sensors signalling via the vagus: descending signals (again via the vagus) then act on the enteric nervous system, resulting in relaxation and dilatation of the fundus and body of the stomach, allowing up to about 1 litre of food to be stored in the stomach with very little rise in pressure.

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8
Q

What is the effect of a vagotomy on accomodation?

A

It doesn’t work any more!

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9
Q

How small do particles in the stomach have to be to pass through the pyloric sphincter?

A

<1-2mm

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10
Q

What is the response of the duodenum to the delivery of acid, amino acids, and lipids?

A

The secretion of hormones CCK, secretin GIP which decrease gastric motility.

Also negative feedback from the duodenum via the enteric nervous system.

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11
Q

What kind of cells can be found lining gastric pits?

A

Mucous cells - also secrete HCO3-

Parietal cells - also called oxyntic cells: secrete HCl and instrinsic factor (fundus and body)

G cell - secrete gastrin (into bloodstream) mainly antrum and pylorus

Chief cells - also call peptic cells, secrete pepsinogen

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12
Q

With which protein may gastrin share receptors?

A

CCK-PZ (C-terminal 5AA the same). Gastrin receptor also called CCK-B receptor.

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13
Q

What stimulates the release of gastrin?

A

Luminal proteins/ AAs

Parasympathetic input (cephalic, and in response to stretch) mediated by gastrin-releasing peptide hormones.

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14
Q

What inhibits the release of gastrin?

A

Luminal H+

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15
Q

What are the main actions of gastrin?

A

Stimulate acid secretion

Promote mucosal growth

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16
Q

From which cells is somatostatin released?

A

D cells of stomach, duodenum and pancreas.

17
Q

What stimulates the release of somatostatin?

A

Luminal H+

18
Q

What inhibits the release of somatostatin?

A

ACh

19
Q

What are the actions of somatostatin?

A

Acts on G cells to inhibit release of gastrin

Also inhibits release of CCK and secretin

20
Q

What is the function of the bicarbonate and mucous secretions?

A

To protect the epithlium from acid.

21
Q

What is the function of instrinsic factor?

A

Binds to cobalamin (B12) in the ileum and facilites uptake.

22
Q

What stimulates the secretion of pepsinogens?

A

ACh, H+, secretin, gastrin, CCK

23
Q

How do pepsinogens become active?

A

Cleave spontaneously at low pH (<5, fast if <3) and also cleaved by pepsin (autolysis).

24
Q

Describe the function of pepsin(s)

A

Endoproteases

Preference for aromatic AAs or large side chains

Optimum pH 2-3

Denatured above 5-7 (once they reach the small bowel)

25
Q

Describe the function of gastric lipase.

A

Cleaves the outer fatty acids - leaves diacyl gylcerol

pH optimum = 4

Stable in stomach but denatured by pancreatic proteases

26
Q

List possible causes of vomiting.

A

Vagal afferents - in response to irritants in or around bowel

Psychogenic (pain, revulsion, fear etc)

Motion sickness/labrynthine disorders

Drugs/toxins with direct effect

Pregnancy

27
Q

What is retching?

A

Involuntary contractions of the diaphragm and abdominal wall muscles.

28
Q

Which part of the stomach may become displaced into the thorax during vomiting?

A

Cardia

GI and metabolism (25 decks)

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