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PHGY 210 > Digestion > Flashcards

Digestion Flashcards

1
Q

what is digestive system made up of (2)

A

GIT and accessory digestive organs

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2
Q

gastrointestinal tract (GIT)

A

alimentary canal = continuous tube from mouth to anus

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3
Q

4 accessory digestive organs

A

salivary glands, pancreas, liver, gall bladder

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4
Q

GIT general function

A

conveys food allowing it to be broken down into small molecules that can be absorbed

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5
Q

6 stages of movement in GIT

A

ingestion
secretion
motility
digestion
absorption
defecation

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6
Q

secretion

A

chemical breakdown by exocrine and endocrine glandular activity

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7
Q

motility

A

muscular activity - propulsion and breakdown

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8
Q

absorption

A

transfer to circulation

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9
Q

GIT is an important contributor to …

A

homeostasis

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10
Q

how does GIT contribute to homeostasis

A

breaks food down into absorbable molecules to provide nutrients to the body

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11
Q

how efficient is GIT for absorbing the 3 food groups

A

99% carbs
95% fat
92% protein

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12
Q

how are the propulsive, secretory and absorptive activities coordinated and integrated for high functional efficiency

A

neural and hormonal mechanisms

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13
Q

GIT structure (2)

A

tubular nature, communication w external environment at both ends

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14
Q

what type of space is the GIT lumen cavity

A

extracellular

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15
Q

how long is GIT in living vs dead

A

4.5m in living (muscular tone)
10m in dead

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16
Q

how many times bigger is GIT than human

A

3x

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17
Q

what is total internal SA of GIT and how many times larger is it than external SA

A

200-250m2 (600x larger)

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18
Q

4 layers of GIT from out to in

A

serosa, muscularis externa, submucosa, mucosa

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19
Q

serosa

A

thin, tough layer of connective tissue (continuous w peritineum in some places)

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20
Q

what is muscularis externa made up of (2)

A

longitudinal and circular fibers

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21
Q

longitudinal fiber contraction =

A

shorten GIT

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22
Q

circular fiber contraction =

A

shrink lumen

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23
Q

what type of muscle is the mouth, upper esophagus and anus

A

striated muscle

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24
Q

what type of muscle is the rest of the GIT

A

smooth muscle

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25
Q

submucosa

A

loose connective tissue containing lymphatics, blood vessels and neuronal network

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26
Q

3 components of mucosa

A

epithelial layer, lamina propria, muscularis mucosae

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27
Q

epithelial layer of mucosa

A

epithelial and glandular cells

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28
Q

lamina propria

A

loose connective tissue

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29
Q

muscularis mucosae

A

smooth muscle

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30
Q

enteric nervous system (ENS)

A

branch of ANS, neurons reside within GIT walls

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31
Q

2 features of ENS

A

independent and integrative

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32
Q

ENS functions

A

initiates, programs, regulates and coordinates activities of muscular, secretory and absorptive elements of GIT

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33
Q

plexus

A

collection of nerve cell bodies

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34
Q

name of plexus between muscularis mucosae and circular muscle

A

submucosa plexus

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35
Q

name of plexus between circular muscle and longitudinal muscle (aka inside muscularis externa)

A

myenteric plexus

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36
Q

how do the 2 plexuses function

A

anatomically distinct but behave as 1 functional unit (ENS)

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37
Q

what do the plexuses contain all the necessary elements for

A

reflex arcs

38
Q

what are the 3 sensory neuron receptors in mucosa/muscle

A

stretch receptors, chemoreceptors, osmoreceptors

39
Q

motor/effector neuron function (in nerve plexus)

A

activate sensory and muscle cells

40
Q

interneuron function (in nerve plexus)

A

expand responses in GIT; allows for integration over longer distances

41
Q

what does ENS consist of

A

ganglion cells and their processes which synapse w smooth muscle cells, endocrine, exocrine cells and other ganglion cells

42
Q

short enteric reflex path (5)

A
  • stimulus
  • sensory receptor (chemo, osmo, mechano)
  • nerve plexus (effector + interneuron)
  • smooth muscle / gland cell
  • response
43
Q

excitatory ENS neurons

A

release ACh on muscarinic receptors

44
Q

inhibitory ENS neurons

A

release NANC (nonadrenergic, noncholinergic) transmitters like NO

45
Q

what are excitatory ENS neurons blocked by

A

atropine

46
Q

where are ENS sensory fibers’ cell bodies

A

in plexuses

47
Q

where do ENS sensory gibers get info from (2)

A

gut chemoreceptors and mechanoreceptors

48
Q

how does ANS synapse onto muscle

A

through ENS, never direct

49
Q

parasympathetic (preganglionic) receptors and effect

A

nicotinic ACh receptors
excitatory

50
Q

sympathetic (postganglionic) receptors and effect

A

noradrenaline receptors
inhibitory

51
Q

autonomic innervation of parasympathetic nerves (2)

A

vagus X and pelvic nerves

52
Q

autonomic innervation of sympathetic nerves (3)

A

celiac ganglion
superior mesenteric ganglion
inferior mesenteric ganglion

53
Q

what do long reflexes modulate

A

short reflex activity (can excite/inhibit for excitatory and inhibtory enteric neurons)
- e.g. excite inhibitory vs excite excitatory

54
Q

what does parasympathetic input lead to

A

vasodilation

55
Q

what does sympathetic input lead to

A

vasoconstriction

56
Q

what is the majority of long reflexes

A

parasympathetic excitation of excitatory ENS neurons

57
Q

what allows for long reflexes

A

sensory neurons

58
Q

3 things to affect CNS

A

emotional state
sight/smell/taste of food
afferent neurons

59
Q

GIT hormones function

A

regulate activities inside GIT (can also influence activities outside GIT)

60
Q

diffuse endocrine system (DES) location & description

A

scattered among other cells in the mucosa; largest most diverse endocrine system in body

61
Q

5 most important GIT hormones

A

gastrin, CCK, secretin, GIP, VIP

62
Q

3 modes of hormonal regulation

A

autocrine, paracrine, endocrine

63
Q

most common mode of hormonal regulation

A

endocrine

64
Q

what type of hormones are most GIT regulatory hormones

A

peptides

65
Q

pathway of GIT regulatory hormones (6)

A

mucosa
hepatic portal vein
liver
heart
systemic circulation
target cells

66
Q

liver function in GIT regulatory hormone pathway

A

filters toxins from gut before sending blood back to heart

67
Q

targets of GIT regulatory hormones

A

multiple (inhibitory + excitatory)

68
Q

how do GIT regulatory hormones interact w each other and with NTs (2)

A

synergistically and antagonistically

69
Q

2 things that drive propulsion in GIT

A

pressure gradients and variations in resistance

70
Q

what causes pressure gradients in GIT

A

coordinated contractions of muscular elements in GIT wall

71
Q

how much resistance is there typically in GIT

A

little to none

72
Q

circular muscles functions (2)

A

segmentation (mixing) and peristalsis (propulsion)

73
Q

sphincters

A

closed at rest (increased resistance point) to prevent movement but open at right time for flow of food

74
Q

3 GIT flow characteristics

A

slow
aboral
meets little/no resistance

75
Q

deglutition

A

swallowing; tightly regulated so food does not move into nose/lungs

76
Q

how many muscles involved in deglutition

A

~20

77
Q

4 phases of deglutition

A

oral
pharyngeal
esophageal
gastric

78
Q

which of the 4 deglutition phases is voluntary

A

oral

79
Q

pharynx function

A

conveys food from mouth to esophagus

80
Q

esophagus function

A

transports food into stomach

81
Q

what does esophagus functioning require

A

relaxation of upper and lower esophageal sphincters

82
Q

oral deglutition phase

A

transport from mouth to pharynx

83
Q

why is oral phase voluntary

A

you can choose to swallow, but once initiated, everything else is reflex

84
Q

cortical center function

A

voluntary movements / ability to initiate

85
Q

medullary center (other name + 2 functions)

A

deglutition center; involuntary reflexes and movement coordination (medulla oblongata)

86
Q

bolus

A

masticated, insalivated mass of food

87
Q

pharyngeal deglutition phase

A

transport from pharynx to esophagus

88
Q

what 2 tracts cross in pharynx

A

respiratory and digestive

89
Q

pharyngeal phase steps (6)

A
  • bolux in pharynx
  • activates stretch receptors
  • reflexes move it downwards
  • presses on epiglottis to cover glottis (airways)
  • reflexive contraction of vocal cords
  • UES relaxes and pharyngeal muscle contracts = push bolus into esophagus
90
Q

soft palate

A

closes off nose cavity

PHGY 210 (3 decks)

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