Physiology and Pharmacology of Gastric Secretion Flashcards

1
Q

what is the volume range of the stomach?

A

50-1000ml depending on whether recently ate or not

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2
Q

how does the stomach expand and relax without changing tension on the walls?

A
ruggae (folds) allow it to expand
receptive relaxation (driven by vagus) to accommodate food from oesophagus
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3
Q

what are the 2 functional areas of the stomach?

A
body/fundus = storage
antrum = grinding
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4
Q

how is the chyme mixed in the stomach?

A

churning action of gastric smooth muscle (peristalsis) pushes chyme against closed pyloric sphincter which forces it back (retropulsion) mixing it around

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5
Q

what determines escape of chyme through the intermittently opened pyloric sphincter?

A

strength of antral wave (peristalsis) which is governed by gastric and duodenal factors

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6
Q

what gastric factors increase the rate of emptying of chyme in the stomach?

A

volume of chyme in stomach
distension (increases emptying due to stretching smooth muscle, stimulates intrinsic nerve plexuses, increases vagus nerve activity - vagal bagal reflex)
consistency of chyme (thinner = faster emptying)

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7
Q

what duodenal factors influence the rate of emptying of chyme in the stomach?

A
neuronal (signals from enteric nervous system decrease antral wave activity)
hormonal responses ( release of enterogastrones from duodenum inhibits stomach contraction via activation of endocrine cells producing secretin and CKK)
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8
Q

what 4 stimuli in the duodenum drive the neuronal and hormonal response?

A

1) fat (delays emptying)
2) acid (delays emptying)
3) Hypertonicity (delays emptying)
4) distension

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9
Q

what are the 2 divisions of the gastric pit which descends through sunmucosa into the lamina propria?

A

pyloric gland area

oxyntic mucosa

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10
Q

what is produced in the pyloric gland area of the gastric pit?

A

D cells release somatostatin

G cells release gastrin

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11
Q

what is produced in the oxyntic mucosa of the gastric pit?

A

chief cells release pepsinogen
parietal cells release HCl, intrinsic factor and gastroferrin
Endochromaffin like cells secrete histamine

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12
Q

what is the function of HCl?

A

activates pepsinogen into pepsin
denatures protein
kills most micro-organisms ingested with food

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13
Q

what is the function of pepsinogen?

A

inactive precursor of pepsin

pepsin, once formed, is autocatalytic so can convert more pepsinogen to pepsin

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14
Q

what is the function of intrinsic factor and gastroferrin?

A

absorption of B12 and iron respectively in duodenum

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15
Q

what is the function of histamine?

A

stimulates HCl secretion

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16
Q

what is the function of mucus?

A

protective

17
Q

what is the function of gastrin?

A

stimulates HCl secretion

18
Q

what is the function of somastatin?

A

inhibits HCl secretion

19
Q

why are the opposing factors gastrin and somastatin both required?

A

HCl only needed when stomach is full