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gastric secretions Flashcards

1
Q

what is secreted in the saliva?

A 
amylase
lysozyme
bicarbonate
growth factors
trans cobalamin II
water
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2
Q

what does amylase do?

A

breaks polysaccharides to disaccharides

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3
Q

what does lysozyme do?

A

lyses bacterial membranes

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4
Q

what does bicarbonate do?

A

neutralizes food and bacterial acids

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5
Q

what do growth factors in the saliva do?

A

stimulate epithelial proliferation to protect the oesophageal epithelium from breaking down.

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6
Q

what does transcobalamin II do?

A

binds to vitamin B12: prevent breaking down stomach

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7
Q

what is found in gastric secretions?

A

mucous, acid, pepsinogen, chymosin, lipase and intrinsic factor

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8
Q

what secretes mucus and what does it do?

A

mucus - coats and lubricates gastric surface and protects the epithelium

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9
Q

what is secreted by parietal cells and what does it do?

A

HCl
activates pepsinogen –> pepsin
inactivates ingested microorganisms

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10
Q

what secretes pepsinogen?

A

mucus cells and chief cells

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11
Q

what does pepsinogen do?

A

activated to pepsin by acid to digest proteins

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12
Q

what secretes chymosin?

A

chief cells

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13
Q

what does chymosin do?

A

coagulates milk protein

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14
Q

what secretes lipase?

A

chief cells

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15
Q

what secretes intrinsic factor?

A

parietal cells and chief cells

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16
Q

what does intrinsic factor do?

A

binds vitamin B12 in the intestine so it can be absorbed

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17
Q

explain how vitamin b12 is absorbed

A 
binds to salivary haptocorrin
complexed with stomach IFs
absorbed in the terminal ileum
transported in portal circulation
transferred to transcobalamin
degraded in lysosome to allow function in metabolism
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18
Q

what do surface mucus cells secrete?

A

mucus, trefoil peptides (associated with mucus), bicarbonate

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19
Q

what is the function of mucus neck cells?

A

stem cell compartment

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20
Q

what do parietal cells secrete?

A

secrete acid and intrinsic factor

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21
Q

what do ECL cells secrete?

A

secrete histamine

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22
Q

what do chief cells secrete?

A

secretes pepsinogen, chymosin and lipase

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23
Q

what do G cells secrete?

A

hormones such as gastrin

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24
Q

explain the process of gastric acid secretion

A

carbonic acid –> CO2 and H2O
H2O –> OH- and H+
CO2 and OH- become bicarbonate ion
H+ pumped into lumen via H+/K+ pump on apical membrane
Cl- pumped into lumen via CFTR channel
HCl formed and turns pepsinogen –> pepsin

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25
Q

where is the H+/K+ pump found?

A

apical membrane of the parietal cell

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26
Q

what are canaliculi and what do they do?

A

secretory network in the parietal cells

transport protons to the top of the cell so it can be secreted through the mucus layer into the lumen

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27
Q

why is mucus important in acid control?

A

acts as a physical and chemical barrier to stop acid from interacting with cells directly

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28
Q

what effect does histamine have on acid secretion and how?

A

stimulates acid secretion by binding to a H2 receptor on parietal cells

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29
Q

what effect does gastrin have on acid secretion and how?

A

activates ECL through CCK2 receptor which stimulates acid secretion

30
Q

explain the role of G cells in acid secretion?

A

detect whether protein rich foods have been digested thoroughly
secrete gastrin

31
Q

what is the function of D cells?

A

monitor acid levels and use somatostatin to regulate acid levels

32
Q

what effect does somatostatin have on acid secretion and how?

A

inhibits acid secretion by inhibiting ECL and parietal cells

33
Q

what effect does ACh have on D cells?

A

stops them from producing somatostatin so that acid can be secreted

34
Q

what complications might occur when NSAIDs are prescribed to a patient and why?

A

stops prostaglandins being produced
increases stomach acid secretion
medication needs to be prescribed to counteract this

35
Q

what causes Zollinger-ellison syndrome?

A

gastric acid hypersecretion

caused by a neuroendocrine tumour

36
Q

what is a gastrinoma?

A

neuroendocrine tumour

37
Q

what part of the body does Zollinger-Ellison syndrome normally affect?

A

duodenum or the pancreas

38
Q

what complications can Zollinger-Ellison syndrome lead to?

A

severe gastroesophageal peptic ulcer disease

39
Q

what are the phases of neural control of gastric secretion?

A

cephalic
gastric
intestinal

40
Q

explain the cephalic phase of neural control of gastric secretions

A

Conditioned reflexes feed into the cerebral cortex –> oral and chemical mechanoreceptors feed into the medullary nuclei –> secretion of acid into the stomach

41
Q

which nervous system is mainly involved in the cephalic phase

A

parasympathetic system

mainly the vagus

42
Q

what is the purpose of the gastric phase?

A

as long as there is food in the stomach (gastric distension), the cycle loops back on itself

43
Q

what is the purpose of the intestinal phase?

A

needed to stop digestion

44
Q

what is the main nerve in the intestinal phase?

A

sympathetic nerves from the spinal cord

vagus has some involvement

45
Q

which two hormones control bile secretion?

A

CCK

secretin

46
Q

what nerve stimulates bile production?

A

parasympathetic impulses along the vagus nerve

47
Q

what organ produces bile?

A

the liver

48
Q

what stimulates the secretion of CCK into the blood?

A

Fatty acids and amino acids in the chyme entering the duodenum

49
Q

what stimulates the secretion of secretin into the blood?

A

Acidic chyme entering duodenum

50
Q

how does CCK impact bile secretion?

A

causes contraction of the gall bladder and relaxation of the sphincter of Oddi

51
Q

how does secretin impact bile secretion?

A

enhances flow of bile rich in HCO3- from liver by stimulating biliary ductal cells

52
Q

what type of bacteria is H. pylori and where is it found?

A

gram negative found in the duodenum and stomach

53
Q

what complications can helicobacter pylori lead to?

A

peptic ulcers

54
Q

describe the stages of H. pylori infection

A

H pylori tunnels through mucus layer to epithelial layer
urease converts water and urea to form CO2 and ammonia
ammonia neutralises gastric acid and de-gels mucin
environment changes
other H pylori can be recruited
mucosal damage
inflammation and cell death

55
Q

how is h pylori infection diagnosed?

A

urea breath test
CLO test
blood antibody test
stool antigen test

56
Q

explain how the urea breath test works

A

urea C14 is given to patient and H. Pylori converts urea C14 to ammonia (NH3) + C14O2

57
Q

explain how the CLO test works?

A 
mucosa biopsy taken from the antrum
put into urea medium with an indicator
urease from h pylori hydrolyses urea to ammonia
raises pH 
colour changes from yellow to red
58
Q

explain the colour changes in the CLO test

A

yellow - negative

red - positive

59
Q

name the treatments for peptic ulcer disease

A

histamine h2 antagonists
proton pump inhibitor
antibiotics

60
Q

name histamine antagonists and explain how they work

A

cimetidine, ranitidine, famotidine

Block H2 receptors on parietal cell
Reduce acid secretion

61
Q

name proton pump inhibitors and explain how they work

A

omeprazole

Prevent H+/K+ ATPase on parietal cell
Reduces acid secretion

62
Q

name antibiotics used to treat peptic ulcer disease and explain how they work?

A

Amoxycillin + Clarithomycin

kill bacteria

63
Q

what treatment of h pylori infection is no longer performed?

A

vagotomy

64
Q

what is GORD?

A

a condition when the reflux of stomach contents causes symptoms and/or complications

65
Q

what is reflux?

A

retrograde flow of gastric contents into the oesophagus

66
Q

what are some of the causes of GORD?

A

excessive reflux - increased frequency of TLOSRs
weakened oesophageal epithelium
hiatus hernia
hypersensitivity of oesophageal pain sensing nerves

67
Q

how is GORD treated?

A

proton pump inhibitors e.g. omeprazole
neurological drugs e.g. baclofen to reduce TLOSRs
Gaviscon and other antacids

68
Q

how do alginates work?

A

forms protective raft over the stomach to prevent acid reflux

69
Q

what is a surgical option for GORD?

A

fundoplication

70
Q

explain how a fundoplication works

A

tightens and reinforces the lower oesophageal sphincter

Upper part of the stomach is wrapped around the outside of the lower oesophagus to strengthen the sphincter

metabolism (23 decks)

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