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VET 405: GI > Meal Phases: Gastric > Flashcards

Meal Phases: Gastric Flashcards

1
Q

stomach

A

dilated part of the canal between esophagus and small intestine

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2
Q

simple stomach

A

single compartment

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3
Q

complex/ruminant stomach

A

multiple compartments

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4
Q

functions of the stomach

A
  1. storage
  2. mixing
  3. H+ secretion
  4. delivery
  5. intrinsic factor secretion
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5
Q

lesser curvature

A

concave curve (along top surface between pylorus and cardia)

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6
Q

greater curvature

A

convex curve (along bottom between fundus and antrum)

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7
Q

lower esophageal sphincter

A

cardiac sphincter; opening between the esophagus and the cardia of the stomach

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8
Q

cardia

A

small area surrounding the LES

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9
Q

function of the LES + cardia

A

prevent reflux
allow entry of food into stomach
regulate belching

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10
Q

secretions in LES and cardiac region

A

mucus and bicarbonate

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11
Q

fundus

A

part of the stomach that extends above the cardia from the cardiac incisure

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12
Q

body of the stomach

A

corpus; extends from the cardia to the angular incisure

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13
Q

function of the fundus and body

A

food reservoir
tonic force during emptying

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14
Q

secretions in the fundus and body

A

H+, IF, mucus, bicarbonate, pepsinogens, lipase

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15
Q

antrum

A

extends from the angular incisure to the pylorus

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16
Q

pylorus

A

pyloric sphincter; opening between the stomach and the duodenum

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17
Q

function of the antrum and pylorus

A

mixing
grinding
sieving
regulation of emptying

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18
Q

secretions of the antrum and pylorus

A

mucus and bicarbonate

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19
Q

rugal folds

A

allow the stomach to expand to accommodate more food

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20
Q

cardiac region histology

A

simple glands that only contain mucin secreting cells

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21
Q

antral region histology

A

enteroendocrine cells + simple glands that only contain mucin secreting cells

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22
Q

body region histology

A

complex gastric glands with many cell types

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23
Q

gastric glands

A

contain parietal and chief cells

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24
Q

gastric pits

A

contain surface/neck cells

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25
Q

surface/neck cells

A

secrete mucin; located in the neck of the gastric gland (gastric pit)

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26
Q

parietal cells

A

secrete acid
located in proximal part of gland
have large canaliculi to maximize transit across cell

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27
Q

chief cells

A

secrete pepsinogen/digestive enzymes
located in distal part of gland
have large, apical granules containing pepsinogen

28
Q

enteroendocrine cells

A

secrete histamine
located throughout the cell

29
Q

steps of acid secretion

A
  1. parietal cells break down H2O –> OH- + H+
  2. carbonic anhydrase produces HCO3-
  3. H+/K+ ATPases pump H+ across the apical side into the stomach lumen (against concentration gradient)
  4. Cl- is pumped into the cell in exchange for HCO3- on basal side; HCO3- enters blood
  5. Cl- crosses the cell and passes into the lumen on the apical side via Cl- channels
30
Q

parietal cell stimulators

A
  1. ACh: released by enteric neurons –> binds to cholinergic receptors on parietal cells
  2. histamine: released by enteroendocrine cells –> bind to H2 receptors on parietal cells
  3. gastrin: released by G cells in response to GRP –> binds to parietal cells and enteroendocrine cells
31
Q

parietal cell inhibitor

A

somatostatin: released by D cells in response to acid in antrum –> binds to G cells to inhibit gastrin secretion –> decreases acid release in antrum

32
Q

steps of pepsinogen secretion

A
  1. H+ in lumen of the stomach stimulates ENS reflex
  2. enteric neurons activate chief cells to release pepsinogen and lipase
  3. pepsinogen gets activated to form pepsin by H+ in the lumen
33
Q

chief cell stimulator

A

ACh: released by enteric neurons –> binds to chief cells

34
Q

vago-vagal reflex

A
  1. sensory neurons detect stretch of gastric wall –> activates parasympathetic outflow to stomach
  2. PS outflow stimulates ENS neurons
  3. enteric neurons stimulate acid and pepsinogen secretion
35
Q

gastric erosion

A

superficial (partial) breakdown of mucosa

36
Q

gastric ulceration

A

full thickness breakdown of mucosa; includes submucosa +/- muscularis

37
Q

causes of ulceration

A

imbalance of aggressive factors and protective factors

38
Q

protective mechanisms of the stomach

A
  1. tight junctions
  2. mucus
  3. bicarbonate
  4. prostaglandins (PGE2)
    - increases blood flow, mucus/bicarb secretions, and epithelial cell proliferation
39
Q

effect of NSAIDs on gastric protection

A

NSAIDs decrease prostaglandin production –> decreased mucosal defense

40
Q

gastric therapies

A
  1. histamine blockers (H2)
  2. proton pump inhibitors (blocks H+/K+ ATPase)
  3. antacids
41
Q

what 3 cell types are needed for GI motility

A

enteric neurons
interstitial cells of cajal (ICCs)
smooth muscle cells

42
Q

slow waves

A

intrinsic electrical activity in smooth muscle; periodic depolarizations that set up electrical conditions for smooth muscle cells to contract in response to ACh release from excitatory myenteric neurons

43
Q

do slow waves reach threshold

A

no

44
Q

what generates slow waves

A

ICCs in pacemaker regions (longitudinal muscle and myenteric plexus)

45
Q

what does the amplitude and frequency of slow waves depend on

A

location in the GI tract
(antrum, small intestine, colon)

46
Q

function of slow waves

A

to organize depolarization events into a pattern of phasic contractions

47
Q

function of gap junctions

A

connect ICCs to other ICCs and smooth muscle cells

areas of low resistance to allow excitatory signal to propagate to neighboring cells

48
Q

what type of ion channels do smooth muscle cells have that allow for contraction

A

L-type Ca2+ channels

49
Q

does excitation spread to ICCs or smooth muscle first

A

ICCs –> coordinates pattern –> sends to smooth muscle

50
Q

what modulates smooth muscle contraction

A

calcium (intra and extracellular)

ICCs set the pattern - action potential fires in same pattern as non-AP generating slow waves

51
Q

what regulates smooth muscle contraction (frequency and tone)

A

enteric nervous system

52
Q

anatomic regions of the stomach

A

fundus, corpus, antrum, pylorus

53
Q

is muscle in the fundus thick or thin

A

thin - mixing function only

54
Q

is muscle in the antrum thick or thin

A

thick - retropulses food back to body and involved in gastric emptying

55
Q

is muscle in the pylorus thick or thin

A

thick - (circular muscle) has tonic contractions to prevent flow

tonic contraction generates HIGH pressure

56
Q

functional regions of the stomach

A

gastric reservoir and gastric pump

57
Q

what type of contractions occur in gastric reservoir region

A

tonic - fundus and body

58
Q

what type of contractions occur in the gastric pump region

A

phasic - antrum

59
Q

steps of gastric motility

A
  1. relaxation of LES and cardia
  2. tonic contraction of LES
  3. relaxation of proximal stomach (fundus and body)
  4. phasic contraction of distal stomach (antrum)
  5. tonic contraction of pylorus
60
Q

steps of gastric emptying

A
  1. tonic contraction of proximal stomach (fundus and body)
  2. increased strength of phasic contractions of antrum
  3. relaxation of pylorus
  4. receptive relaxation of SI (inhibits duodenal contraction)

creates high pressure in stomach and low pressure in SI –> liquids/semi-liquid chyme flows from high to low pressure

61
Q

predominant reflex during gastric phase

A

receptive relaxation

62
Q

regulation of gastric emptying

A

allows gastric emptying to slow depending on nutrient/energy content of food to maximize nutrient absorption

afferents:
enteroendocrine cells & vagal afferents: sense nutrients, H+ and hyperosmolarity of food

efferents:
activation of vagal outflow decreases strength of antral contractions, contracts pylorus, and decreases proximal motility to SLOW gastric emptying

63
Q

sieving function of stomach

A

liquids empty faster than large particles
- can empty through SMALL pyloric opening
- large particles get pushed back

64
Q

rate of liquid emptying

A

exponential rate

65
Q

rate of solid emptying

A

lag phase followed by linear rate

66
Q

how stomach increases rate of emptying

A
  1. tonic contraction of reservoir
  2. deep peristaltic waves of body
  3. deep contractions of antral waves
  4. wide pyloric opening
  5. duodenal receptive relaxation
67
Q

how stomach decreases rate of emptying

A
  1. prolonged relaxation of reservoir
  2. shallow peristaltic waves of body
  3. shallow antral waves
  4. small pyloric opening
  5. lack of duodenal relaxation

VET 405: GI (19 decks)

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