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gastrointestinal > stomach > Flashcards

stomach Flashcards

1
Q

what is deglutition

A

swallowing = propulsion of food from oral cavity into oesophagus

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2
Q

process of swallowing

A

food molded into bolus by tongue and moved upwards and backwards to pharynx - forces soft palette up to seal of nasal cavity - voluntary
pressure-sensitive sensory cells stimulated
swallowing centre in medulla initiates swallowing reflex - involuntary
epiglottis closes off trachea
complicated contraction/relaxation of muscles forces food into oesophagus

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3
Q

what are the layers of the oesophagus

A

mucosal
submucosal
muscular
serosal

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4
Q

what is the mucosal layer composed of

A

stratified squamous epithelium

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5
Q

what is the muscular layer composed of

A

striated and smooth muscle

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6
Q

what is the serosal layer composed of

A

adventitia - loose connective tissue only in neck

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7
Q

what is the process of food being transported down the oesophagus

A

upper oesophageal sphincter closes behind food bolus
complicated peristaltic contractions force food down oesophagus
lower oesophageal sphincter opens to allow passage of food into stomach

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8
Q

what is the lower oesophageal sphincter

A

cardiac sphincter
physiological - except in horses = anatomical
prevents regurgitation of acidic stomach contents

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9
Q

what is emesis

A

vomiting - active propulsion of stomach contents into oral cavity

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10
Q

where is the vomiting centre

A

medulla

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11
Q

what is vomiting stimulated by

A

pharyngeal/gastric distension or irritation

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12
Q

what is gastric torsion

A

stomach rotates 90-360 degrees
seals off cardiac sphincter preventing vomiting

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13
Q

what animals does gastric torsion occur in

A

horses and dogs with wide chests

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14
Q

what happens if rotation compromises blood supply in gastric torsion

A

gastric tissue becomes hypoxic and in severe cases necrotic

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15
Q

what are the functions of the simple stomach

A

digestion
protection
storage
mechanical breakdown

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16
Q

what is the ruminant equivalent of the simple stomach

A

abomasum

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17
Q

what is the embryological regions of the stomach and what do they secrete

A

oesophageal - non-glandular, stratified squamous epithelium
cardiac - mucous
fundic -mucous and gastric juices
pyloric - mucous

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18
Q

what is the cardia region

A

entrance to stomach

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19
Q

what is the fundus

A

blind-ending part

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20
Q

what is the corpus

A

body of stomach

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21
Q

what is the pylorus

A

exit from stomach

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22
Q

stomach cell types

A

mucous
parietal
chief
entero-endocrine

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23
Q

function of mucous cells (goblet)

A

secrete mucus to protect against HCL

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24
Q

function of parietal cells (oxytinic)

A

secrete HCL to digest protein

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25
Q

function of chief cells (peptic)

A

secrete pepsinogen to digest protein

26
Q

function of entero-endocrine cells

A

secrete hormones

27
Q

what does motility do

A

prepare stomach to receive a meal
mix and mechanically break down chyme
empty stomach contents into small intestine
prevent regurgitation of stomach contents into oesophagus

28
Q

what is the transmitter that allows initial relaxation of stomach smooth muscle to accommodate the meal

A

vasoactive intestinal peptide

29
Q

what is the main type of contraction involved in motility

A

peristalsis

30
Q

process of motility

A

fundus weak contractions
propogate down corpus
pyloric sphincter opens to allow chyme into duodenum
when contraction reach pylorus the pyloric sphincter closes
food forced back into corpus helps mixing

31
Q

what is stomach emptying regulated by

A

strength of contraction
opening/closing of pyloric sphincter
stimulation and inhibition of emptying

32
Q

what stimulates emptying of stomach

A

neural regulation - expansion of stomach increases strength of contraction
hormonal regulation - release of gastrin increases strength of contraction and dilates pyloric sphincter

33
Q

what inhibits emptying of the stomach

A

increased pressure in duodenal walls, low PH, high fat/peptide contraction, high osmolarity.
neural regulation by increased sympathetic activity/decreased parasympathetic activity
hormonal regulation via secretin, CCK and GIP.

34
Q

what is digestion

A

enzymatic breakdown of nutrient macromolecules into smaller units that can be absorbed

35
Q

what is starch digested by and at what pH

A

amylase
only active at pH greater than 6

36
Q

what is protein digested by and at what pH

A

pepsin
active at low pH

37
Q

what is starch made from

A

amylose and amylopectin - complex carb

38
Q

what is starch digestion initiated by

A

salivary amylase in mouth

39
Q

what allows starch digestion to continue for a while

A

acid secreted from stomach walls so gradual decline in pH from centre of stomach to edge

40
Q

level of starch in omniverous diets

A

high

41
Q

level of starch in herbiverous diets

A

low

42
Q

levels of starch in carniverous diets and why

A

low - saliva does not contain amylase

43
Q

what does pancreas also produce

A

amylase

44
Q

what does gastric juices consist of

A

HCL and pepsinogen (inactive form of pepsin)

45
Q

what leads to ulceration

A

breach of mucosal barrier

46
Q

functions of HCL

A

convert inactive pepsinogen into active form pepsin
provides required acidic environment for pepsin to digest protein
prevents fermentation by killing microbes
degrades large chunks of connective and muscle tissue into smaller more digestible particles

47
Q

when does maximum secretion of HCL occur

A

2-3 hours after a meal

48
Q

what is duration and volume of HCL dependent on

A

species
dog produce 0.5-1L per hour where as horse produces 20-30L

49
Q

why does urine pH increase after a meal

A

delay between food passing stomach to pancreas

50
Q

how does pepsin initiate degradation of protein and collagen

A

breaking peptide links adjacent to aromatic amino acids

51
Q

what can pepsin activate

A

more pepsinogen

52
Q

what stimulates secretion

A

reflex arcs - long via vagus and short locally
histamine, chief, parietal and mucin cells amplify each other
gastrin

53
Q

what is cephalic phase caused by

A

sight, smell, taste, presence of food in mouth

54
Q

what does cephalic phase stimulate and how

A

secretion
directly via acetylcholine
indirectly via gastrin in blood

55
Q

what is gastric phase caused by

A

stomach expansion
peptides in lumen

56
Q

what does gastric phase stimulate

A

secretion
directly via acetylcholine
indirectly via gastrin in blood

57
Q

what is stimulation/inhibition in the intestinal phase dependent on

A

acidity of chyme
food components

58
Q

how is intestinal phase stimulated

A

neural (cholinergic) and hormonal (gastrin and CCK) signals

59
Q

what are most intestinal responses

A

inhibitory

60
Q

what is hormonal stimulation mediated by

A

gastrin

gastrointestinal (10 decks)

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