L3- Stomach secretions Flashcards

1
Q

functions of the stomach

A
  • store food
  • regulates the release the contents into the duodenum
  • mix the food with the gastric secretions
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2
Q

what is the inner lining called in stomach and in other organs

A

mucosa

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3
Q

function of mucous neck cell

A
  • mucous neck cell- produces mucous and bicarbonate fluid to protect from injury and acid erosion

-

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4
Q

function of parietal cell

A

secretes acid and intrinsic factor ( for absorbing food)

-predominantly found in the corupus region

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5
Q

function of chief cell

A

secretes pepsinogen whhich is a precursor for pepsin

- predominantly found in the corupus region

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6
Q

function of ECL like cells

A

secretes histamine to trigger acid secretion

- in corpus region

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7
Q

function of d cells

A

secretes somatostatin for acid secretion

-found in corupus, antrum and pylorus region of the stomach

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8
Q

function of G cells

A

secretes gastrin for acid secretion

- found in antrum and pylorus region of the stomach

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9
Q

what happens when a parietal cell is stimulated

A
  • CO2 diffuses into the cell
  • joins with water to make carbonic acid caytalsed by carbonic anhydrase
  • the acid dissociates into H+ ion and HCO3-
  • HCO3 transported out into the blood in exchange of CL- ions, resulting in alkaline tide in the plasma
  • H ions transported out into the lumen in exchange for K+ ions through ATPase.
  • now the acid is produced in the lumen
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10
Q

how does gastrin regulates acid secretion

A
  • gastrin - stored in vesicles along the basolateral membrane of the cell and gets released through vagal stimulation
  • increases expression of protom pumps in the parietal cells in the antrum
  • gastrin binds to ecl cell to stimulate histamine synthesis and the histaine act upon the H2 receptors on pareital cells to release acid
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11
Q

what part of the nervous systems control the functions of the stomach

A
  • ENS through vagus and sympathetic nerves
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12
Q

how can ACH act upon acid secretion

A
  • stimulates parietal cells to release acid and G cells to release gastrin
  • stimulates ECL cells to release histamine
  • stimulates D cells to inhibit somatostatin release

– ACH stimulates G cells which then stimulates parietal cell directly and indirectly via ECL cell

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13
Q

triggers for acid secretion

A

gastrin, histamine, ACH,

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14
Q

inhibitory factors for acid secretion

A
  • somatostatin
  • CCK
  • secretin
  • VIP and GIP
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15
Q

how does secretin act upon the acid secretion inhibition

A
  • inhibits gastrin release and acid secretion

- stimulated by the acid in the duodenum

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16
Q

how does somatostatin act upon the acid secretion inhibition

A
  • due to high levels of gastrin in the blood, the somatostatin is released from the d cells
  • inhibits gastrin from G cells and histamine secretion from ECL cells
17
Q

how does VIP and GIP act upon the acid secretion inhibition

A

acts on the same receptors for secretin on the parietal cells to stop acid release

18
Q

how does CCK act upon the acid secretion inhibition

A
  • produced by I cells in the duodenum and jejunum in response to fat.
  • reduces acid release from parietal cells by acting as an antagonist for the acid secretion
19
Q

pharmacoloigcal inhibitors for acid secretion

A
  • proton pumps inhibitors

- H2 receptors anatagonists which are competitive against histamines at the parietal cells receptors

20
Q

4 phases of gastric acid secretion

A

-basal, cephalic, gastric, intestinal

21
Q

what is basal phase

A

where the acid secretion follows circadian rhythm

  • so its low at a.m and high at p.m
  • enchanced even higher by eating
22
Q

what is cephalic phase

A

a response to an approach of food before it reaches the mouth like by smell, sight, taste, thought.
-gastric acid and pepsinogen activated

23
Q

what is gastric phase

A

when the food enters the stomach
- more than 50% acid secretion
-

24
Q

what is intestinal phase

A

food mixed with secretions from pancreas and liver

  • gastrin secretion and gut motility inhibited
  • acidic fluid in the small intestine from the stomach cause a release of secretin and other factors inhibit acid secretion
25
Q

why is it important to inhibit acid secretion once the food enters the duodunum

A
  • digestive enzymes requires neutral or near acidic Ph for optimum activity
  • micelle formation for fat digestion and absorption can take place at neutral or near acidic pH
  • reduces risks for ulcers
26
Q

what does pepsinogens do in the digestion

A

initiates protein digestion

27
Q

why is prostaglandins helpful protecting gastric muscosa

A
  • inhibits acid secretion
  • stimulates HCO3 release to neutralise the acid
  • secretes mucus
28
Q

what does H pylori do

A

produces urease

  • converts urea into other products then into HCO3 and NH4+
  • the HCO3 neutralises the stomach acid
29
Q

what happens if there is H.p infection in the antrum

A
  • G cells secretes gastrin too much
  • and decrease somatostatin release
  • so too acid is produced
  • this is hypergastrinaemia
30
Q

what happens if there is H.p infection in the corpus

A
  • gastric ulcers and reduces acid secretion
    so there is a loss of acid
  • this is hypochlorhydria
31
Q

why is intrinic factor important

A
  • produced by the parietal cells

- important to absorb Vit B12 otherwise results in health consequences