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gastric secretions Flashcards

(70 cards)

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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
where is the H+/K+ pump found?
apical membrane of the parietal cell
26
what are canaliculi and what do they do?
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
27
why is mucus important in acid control?
acts as a physical and chemical barrier to stop acid from interacting with cells directly
28
what effect does histamine have on acid secretion and how?
stimulates acid secretion by binding to a H2 receptor on parietal cells
29
what effect does gastrin have on acid secretion and how?
activates ECL through CCK2 receptor which stimulates acid secretion
30
explain the role of G cells in acid secretion?
detect whether protein rich foods have been digested thoroughly secrete gastrin
31
what is the function of D cells?
monitor acid levels and use somatostatin to regulate acid levels
32
what effect does somatostatin have on acid secretion and how?
inhibits acid secretion by inhibiting ECL and parietal cells
33
what effect does ACh have on D cells?
stops them from producing somatostatin so that acid can be secreted
34
what complications might occur when NSAIDs are prescribed to a patient and why?
stops prostaglandins being produced increases stomach acid secretion medication needs to be prescribed to counteract this
35
what causes Zollinger-ellison syndrome?
gastric acid hypersecretion | caused by a neuroendocrine tumour
36
what is a gastrinoma?
neuroendocrine tumour
37
what part of the body does Zollinger-Ellison syndrome normally affect?
duodenum or the pancreas
38
what complications can Zollinger-Ellison syndrome lead to?
severe gastroesophageal peptic ulcer disease
39
what are the phases of neural control of gastric secretion?
cephalic gastric intestinal
40
explain the cephalic phase of neural control of gastric secretions
Conditioned reflexes feed into the cerebral cortex --> oral and chemical mechanoreceptors feed into the medullary nuclei --> secretion of acid into the stomach
41
which nervous system is mainly involved in the cephalic phase
parasympathetic system | mainly the vagus
42
what is the purpose of the gastric phase?
as long as there is food in the stomach (gastric distension), the cycle loops back on itself
43
what is the purpose of the intestinal phase?
needed to stop digestion
44
what is the main nerve in the intestinal phase?
sympathetic nerves from the spinal cord | vagus has some involvement
45
which two hormones control bile secretion?
CCK | secretin
46
what nerve stimulates bile production?
parasympathetic impulses along the vagus nerve
47
what organ produces bile?
the liver
48
what stimulates the secretion of CCK into the blood?
Fatty acids and amino acids in the chyme entering the duodenum
49
what stimulates the secretion of secretin into the blood?
Acidic chyme entering duodenum
50
how does CCK impact bile secretion?
causes contraction of the gall bladder and relaxation of the sphincter of Oddi
51
how does secretin impact bile secretion?
enhances flow of bile rich in HCO3- from liver by stimulating biliary ductal cells
52
what type of bacteria is H. pylori and where is it found?
gram negative found in the duodenum and stomach
53
what complications can helicobacter pylori lead to?
peptic ulcers
54
describe the stages of H. pylori infection
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
how is h pylori infection diagnosed?
urea breath test CLO test blood antibody test stool antigen test
56
explain how the urea breath test works
urea C14 is given to patient and H. Pylori converts urea C14 to ammonia (NH3) + C14O2
57
explain how the CLO test works?
``` 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
explain the colour changes in the CLO test
yellow - negative | red - positive
59
name the treatments for peptic ulcer disease
histamine h2 antagonists proton pump inhibitor antibiotics
60
name histamine antagonists and explain how they work
cimetidine, ranitidine, famotidine Block H2 receptors on parietal cell Reduce acid secretion
61
name proton pump inhibitors and explain how they work
omeprazole Prevent H+/K+ ATPase on parietal cell Reduces acid secretion
62
name antibiotics used to treat peptic ulcer disease and explain how they work?
Amoxycillin + Clarithomycin kill bacteria
63
what treatment of h pylori infection is no longer performed?
vagotomy
64
what is GORD?
a condition when the reflux of stomach contents causes symptoms and/or complications
65
what is reflux?
retrograde flow of gastric contents into the oesophagus
66
what are some of the causes of GORD?
excessive reflux - increased frequency of TLOSRs weakened oesophageal epithelium hiatus hernia hypersensitivity of oesophageal pain sensing nerves
67
how is GORD treated?
proton pump inhibitors e.g. omeprazole neurological drugs e.g. baclofen to reduce TLOSRs Gaviscon and other antacids
68
how do alginates work?
forms protective raft over the stomach to prevent acid reflux
69
what is a surgical option for GORD?
fundoplication
70
explain how a fundoplication works
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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