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fluids and metabolism > gastric secretion > Flashcards

gastric secretion Flashcards

1
Q

what are the three functions of the stomach

A

stores food for 2-4 hours
secretes gastric juices
allows emptying of food into small intestine

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2
Q

what are the five sections of the stomach called

A

cardia
fundus
body
antrum
pylori

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3
Q

explain what the cardia is

A

top section of the stomach contains a cardiac spincter that prevents food from going back into esophagus

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4
Q

what is the fundus

A

rounded section next to cardia below diaphragm

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5
Q

what is the body corpus

A

largest part of stomach, stomach contracts and begins to mix food

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6
Q

what is the antrum

A

lies below the body holds food until stomach is ready to send it to your small intestine

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7
Q

what is the pylorus

A

bottom part of stomach it includes pyloric spincter
pyloric sphincter- is a ring of tissue that controls when and how your stomach contents move into your small intestine

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8
Q

what are the layers of the stomach

A

mucosa
sub mucosa
muscularis
serosa

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9
Q

explain what mucosa is

A

stomachs inner lining when stomach is empty mucosa has small ridges called rugae. when stomach is full mucosa expands and the ridges flatten

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10
Q

explain what submucosa is

A

contains connective tissue, blood vessels, lymph vessels, it covers and protects mucosa

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11
Q

explain what muscularis externa is

A

primary muscle of stomach it has three layers to contract and relax break down food

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12
Q

explain what serosa is

A

a layer of membrane that covers your stomach

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13
Q

what is significant about pyloric antrum

A

major area of endocrine secretion production and release of gastrin

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14
Q

what are the two types of exocrine glands

A

gastric glands and pyloric glands

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15
Q

where are gastric glands in the stomach

A

fundus and body

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16
Q

where are pyloric glands found in the stomach

A

antrum

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17
Q

what type of cells do gastric glands contain

A

surface mucous cells
mucus neck cells
parietal cells
enterochromaffin like cell (histamine)
d cell somatostatin
chief cell- pepsinogen

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18
Q

what type of cells do pyloric glands contain

A

surface mucous cell
mucous neck cell
g cell gastrin
d cell somatostatin

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19
Q

what is gastric secretion composed of

A

2L gastric secretion/ day
isotonic PH 2-3
hcl: kills bacteria, denatures dietry protein, activates pepsinogen, cofactor for pepsin action
pepsin- initiates protein digestion
instrinsic factor- essential for vitamin b12 uptake in lower ileum

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20
Q

how is hcl produced in parietal cells

A
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21
Q

what are subcellular changes in the parietal cell during acid secretion
resting
active state

A

resting state- tubulovesicles
active state- canaliculus

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22
Q

where is pepsinogen secreted from and how is it secreted

A

pepsinogen is released from chief cells in the gastric glands
pepsinogen is a zymogen it has a masking sequence which is removed at a lower ph exposing the active site.
pepsinogen and hcl are secreted into the lumen, hcl converts pepsinogen into pepsin as it is a cofactor

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23
Q

what is the function of pepsin

A

endopeptidase and it initiates protein digestion
responsible for 15% of protein digestion
a ph less than 2 is required for optimum proteolytic activity

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24
Q

how is intrinsic factor released

A

intrinsic factor is a glycoprotein secreted from parietal cells.
it forms a complex with dietry b12 in the upper small intestine which protects it fro enzymatic digestion
it is the only gastric secretion that is essential for life as b12 is needed for maturation of erythrocytes and maintenance of cns
absence of intrinsic factor causes pernicous anaemia

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25
how is b12 absorbed with the involvement of intrinsic factor
intrinsic factor and dietry b12 form a complex in the duodenum, intrinsic factor protects b12 from enzymatic digestion, the intrinsic factor and b12 complex reaches mucosal cell in terminal ileum, receptor mediated endocytosis, complex is endocytosed and intrinsic factor broken down within cell, b12 delivered into circulation and binds to b12 binding protein in the plasma, and the complex is delivered to the liver where it can be stored for up to 3 years.
26
what three systems control gastric secretion
parasympathetic control endocrine- gastrin paracrine- histamine somatostatin
27
how does autonomic control of gastric secretion work
parasympathetic increases secretion via direct and indirect mechanisms sympathetic- no major control over secretion enteric nervous system-submucosal and myenteric plexus increases secretion
28
what are the effects of increased neurocrine activity
hcl production pepsinogen release gastrin release mucous release gastric smooth muscle contraction
29
how does endocrine of gastric secretion work
gastrin is the main endocrine hormone that promotes gastric secretion it increases- hcl production, pepsinogen release, mucous release and maintenance of gastric mucosal structure and increases motility of gi smooth muscle
30
how are paracrine hormones involved in gastric secretion
histamine-stimulates hcl, parietal cells somatostatin-inhibits hcl secretion, direct effects on parietal cells, inhibiting release of the positive regulators histamine and gastrin
31
what is the receptor that somatostatin binds to
sstr and what does it act on camp
32
what receptor does histamine bind to
h2 and what does it act on camp calcium
33
what receptor does gastrin bind to
cck2 and what does it act on calcium
34
what receptor does ach bind to
m3 and what does it act on calcium
35
give an example of a proton pump inhibitor
omeraprazole
36
give an example of a h2 antagonist
famotidine
37
what are the three phases of gastric secretion
cephalic gastric intestinal
38
what percentage of total secretion in cephalic phase
30-35
39
what percentage of total secretion in gastric phase
60
40
what percentage of total secretion is intestinal phase
20-10%
41
what is the cephalic phase of gastric secretion
occurs before food enters the stomach short duration
42
what is the function of the cephalic phase of gastric secretion
prepares stomach for receiving food stimuli- anticipation, sight,, chewing smell of food
43
what are components of cephalic phase of gastric secretion
direct vagal stimulation and activation of submucosal plexus indirect- release of gastrin from g cells and subsequent stimulation of parietal cells
44
what do submucosal plexus innervate
they innervate mucous cells to secret mucous, chief cells to release pepsniogen g cells to secrete gastrin and parietal cells to secrete hcl
45
what are the components of the cephalic phase
direct- vagal stimulation and activation of submucosal plexus indirect- release of gastrin from g cells and subsequent stimulation of parietal cells.
46
what is the gastric phase of gastric secretion
occurs while food is in the stomach 2-4 hours long
47
what is the function of the gastric phase
homogenises and acidifies chyme, initiates digestion of protein by pepsin
48
what is the stimuli for the gastric secretion phase
distension, elevated ph and peptides amino acids in the stomach
49
what are components of gastric phase
distension initiates vago-vagal and enteric reflexes causing direct and indirect effects on parietal cells peptides cause secretion of gastrin low luminal ph inhibits secretion
50
what is the intestinal phase of gastric secretion
occurs when the chyme enters the duodenum largely hormonal long duration hours
51
what is the function of intestinal phase
controls the rate of chyme entry into the duodenum
52
what is the stimulus of the intestinal phase
duodenal stretch, presence of lipids and carbohydrates and decreased lipids
53
what are the components of the intestinal phase
initial short lived stimulation of gastric secretion caused by gastrin release from g cells in the duodenum in response to peptides in the chyme release of cholesystokinin and secretin have an inhibitory effect on acid secretion and gastric emptying
54
with all the acid present why doesnt the stomach digest itself
because of gastric mucosal barrier
55
how thick is the gastric mucosal barrier in fasting state
5 micrometeres thick
56
how thick is the gastric mucosal barrier in the digestive phase
200 micrometers
57
what is the effectiveness of the mucosal barrier reduced by
aspirin helicobacter pylori leads to gastritis ulceration
58
what do surface mucus cells secrete
alkaline mucus
59
where are surface epithelial cells found
facing the stomach lumen, found in stomach lining
60
how do surface epithelial cells play a crucial role in secretion and protection of stomach lining
surface epithelial cells secrete mucus that trap hydrogen bicarbonate, hydrogen bicarbonate is secreted into mucus layer, the hydrogen bicarbonate ions react with hydrogen ions forming carbon dioxide and water and so neutralises mucous lining
61
what is the origin of hydrogen carbonate for secretion by surface mucous cells
hydrogen secretion is accompanied by delivery of hydrogen carbonate into perfusing blood (alkaline tide) this hydrogen carbonate is is carried to the surface epithelium where it is secreted into the surface mucosal layer
62
what are duodenal ulcers
usually occur in the duodenum 50% are found in the anterior wall 4 times more common than gastric ulcers more common in males risk factors helicobacter pylori nsaids lifestyle
63
what are gastric ulcers
less common than dudodenal ulcers
64
what are risk factors for gastric ulcers
n said use- most common bile reflux helicobacter pylori
65
what is zollinger ellison syndrome
a rare condition caused by excessive gastric secretion by a tumour of non beta cells of pancreatic islets uncontrolled gastrin release causes very high levels of gastric acid secretion this causes multiple ulcers mainly in distal duodenum symptoms- abdominal pain, diarrhoea, steatorrhea

fluids and metabolism (16 decks)

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