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Gastrointestinal > gastric physiology > Flashcards

gastric physiology Flashcards

1
Q

functions of stomach min 5

A 
Store and mix food
Dissolve and continue digestion
Regulate emptying into duodenum
Kill microbes
Secrete proteases 
Secrete intrinsic factor
Activate proteases
Lubrication
Mucosal protection
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2
Q

surface of gastric mucosa cells

A

mucous cells

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3
Q

where is gastric acid made

A

fundus and body of stomach

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4
Q

names of the three phases of gastric acid secretion

A

cephalic phase
gastric phase
duodenal phase

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5
Q

what to g cells make and their function

A

gastrin stimulate secretion of hcl and histamine

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6
Q

what does ach do in the cephalic phase - turning it on

A

acts on parietal cells to turn them on and triggers the release of gastrin and histamine

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7
Q

What do d cells make derek for

A

derek for somastin

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8
Q

gastric phase for the production of gastric acid ?

A 
g cells release gastrin 
acts on parietal cells
gastrin triggers release of histamine 
histamine acts directly on parietal cells
net goal= to increase acid production
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9
Q

function of proteins in the lumen

A

act as a buffer , mopping up H+ ionss causing ph to rise ,decreased secretion of somatostatin
more parietal cell activity due to lack of inhibition

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10
Q

how to stop gastric phase

A

low luminsl ph inhibits gastrin secretion via a negative feedback loop
inhibits histamine via gastrin
stimulates somastatin release inhibits parietal cell activity

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11
Q

turning off in the intestinal phase

A

Presence of chyme in duodenum stimulates entero endocrine cells to release cholecystokinin and secretin
Inhibit gastric acid secretion

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12
Q

which nerve innervate ach

A

VAGUS NERVE

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13
Q

what is a peptic ulcer

A

a breach in the musocal surface

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14
Q

causes of peptic ulcers

A

Helicobacter pylori infection
Drugs – NSAIDS
Chemical irritants – alcohol, bile salts, ? Dietary factors
Gastrinoma

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15
Q

treatment for peptic ulcers

A

tablets for one week

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16
Q

how does gastric mucosa defend itself

A

alkaline mucus
Tight junctions between epithelial cells
Replacement of damaged cells
Feedback loops

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17
Q

what does Helocobacter pylori do to cause peptic ulcer and treatment

A

Secretes urease , split urea into co2 and ammonia
Treatment - proton pump inhibitor to lower on
Followed by antibiotics

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18
Q

how do NSAID’s work to cause peptic ulcer

A

Inhibit cox-1
Reduced production of prostaglandin
More mucosal injury

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19
Q

how do bile salts cause peptic ulcer

A

Duodeno-gastric reflux
Regurgitated bile strips away mucus layer
Reduced mucosal defence

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20
Q

what cells produce pepsinogen

A

chief cells

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21
Q

what enzyme does the stomach produce

A

NO ENZYME

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22
Q

protease activation

A

positive feedback loop
pepsinogen into pepsin via HCL.
Pepsin is very ph dependant

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23
Q

how does pepsin help in protein digestion

A

breaks down collagen into meat, helps shred meat into smaller pieces , greater surface area

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24
Q

peristalsis

A

peristalsis waves- contractions weak at fundus and cardia then towards pylorus they become stronger and then closes

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25
Q

What do the interstitial cells of cajal do

A

Pacemaker cells
Control the frequency of contractions
3 a minute

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26
Q

what happens if you overfill the duodenum

A

dumping syndrome, vommiting , cramps, diarrhoea

27
Q

gastroparesis

A

delayed gastric emptying

28
Q

effects of gastroparesis

A

nausea, anorexia, abdo pain, vomit undigested food

29
Q

Gastric acid secretion step by step

A

H20 and co2 combine to produce carbonic acid catalysed by carbonic anhydrase
Carbonic acid dissociates into h+ and bicarbonate ion
H+ moves into stomach via action be transport
HCO3- out the cell and swap with cl-
H and cl to make hcl

30
Q

How to increase gastric acid production 2 ways

A

1)Via ach released from the vagus nerve
Direct stimulation of parietal cells
Produced during gastric phase where intrinsic nerves detect distension stimulating ach

2)activation of g cells leads to gastric release
Gastrin released and binds to CCK receptors on parietal cells which elevates calcium levels causing increased vesicular fusion.

31
Q

How does pepsinogen get converted to pepsin

A

By hcl

32
Q

functions of the colon

A

Absorption of water and electrolytes
Production of vitamins
Excretion of waste

33
Q

start oof the bowel

A

ileocaecal valve/ junction

34
Q

layers of the colonic wall

A

Mucosa
Submucosa
Muscularis propria
Serosa

35
Q

histology of colon

A

columnar epithelium , goblet cells

36
Q

what is the gastro-colic- reflex

A

Stomach stretching and food in the jejunum leading to mass movement of the colon

37
Q

How do we know we need a poo?

A

Rectum fills
Reflex relaxation of internal anal sphincter
Sampling reflex

38
Q

To complete defaecation

A

External sphincter relaxes
Puborectalis relaxes
Rectum contracts
Valsalva maneuver

39
Q

What do enterochromaffin ecl cells secrete

A

Histamine

40
Q

What do H2 receptors do

A

Histamine binds to them Causing increased gastric aid production in stomach

41
Q

How many layers of muscle in the stomach

A

3

42
Q

two functions of pancreas

A

Endocrine secretion

Exocrine secretion
Aqueous bicarbonate secretion
Enzyme secretion

43
Q

what does the enyzme cholecystokinin do

A

Gallbladder contraction
Inhibition of gastric acid secretion
Delays gastric emptying

44
Q

where is the enzyme Cholecystokinin produced

A

I cells of duodenum & jejunum

45
Q

How does secretin inhibit gastrin and reduce gastric acid production

A

Release of somastatin

Inhibits release of gastrin in the pyloric antrum

46
Q

action of the enzyme gastrin

A

HCl secretion (parietal cells) enzyme release (acinar cells)

47
Q

consequences of exocrine dysfunction

A

malnutrition, osteoporosis, increased cardiovascular morbidity,

48
Q

protein digestion ?

A

Pepsin initiates in stomach. Trypsin & Chymotrypsin packaged into secretory vesicles as proenzymes; prevents auto digestion
Enterokinase embedded in Smallintestine mucosa. Active trypsin activates chymo and trypsinogen

49
Q

what is a mesentery

A

The mesentery attaches your intestines to the wall of your abdomen.

50
Q

How to work out bmi

A

Weight / height 2

51
Q

What is bmr

A

Basal metabolic rate

The amount of energy needed to stay alive at rest

52
Q

What can increase your bmr

A

Being overweight
Male
Pregnancy
Exercise

53
Q

What can decrease your bmr

A

Increase in age
Malnutrition
Starving
Hypothyroidism

54
Q

How is gastric acid produced

A

Parietal cells have a proton pump that release protons in exchange for k , proton binds with cl in lumen

Ecf cells release histamine which bind to h2 receptors on parietal cells for more proton release

Gastrin also promoted hcl production

55
Q

Layers of the stomach

A

Mucosa
Submicosa
Muscularis externa
Serosa

56
Q

What happens in the cephalic phase

A

Activated upon seeing , smelling food etc
Stimulation via vagus nerve and ach
Ecl cells secrete histamine , g cells also release gastrin

57
Q

What happens in the gastric phase

A

Stomach distension
Triggers gastrin release , activates histamine release
Hcl continues to be secreted in response to distension and amino acids digested due to proteases

58
Q

What happens in the intestinal phase

A

Duodenum initially enhances gastrin secretion but soon inhibits it
Enterogastroc reflex, duodenum sends inhibitory impulses to the stomach

59
Q

What is gastric motility mediated by

A

Acetylcholine , parasympathetic vagus nerve

Nitric oxide serotonin

60
Q

What increases the strength of gastric contractions

A

Gastrin

Distension of stomach

61
Q

What decreases the strength of gastric contractions

A

Duodenal distension
Increase in duodenal fat
Decrease in duodenal fat
Increase sympathetic stimulation

62
Q

Role of pepsinohgen

A

Pepsinogen as an inactivate Zymogen of Pepsin
Activated by low ph
Increase protein digestion
Shreds meat

63
Q

What is gastric motility

A

Peristaltic contraction

64
Q

Difference between large and small intestine

A

Small
Smaller
No appendices
Wall smooth

Large 
Larger 
Longitudinal muscle is not continuous 
Has appendices 
Sacculated

Gastrointestinal (8 decks)

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