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PHGY 210 > digestion > Flashcards

digestion Flashcards

1
Q

what is the GIT?

A

alimentary canal that is continuous tube from the mouth to anus

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2
Q

What is the main function of the GIT?

A

Conveys food along GIT allowing it to be broken down into small molecules which can be ansorbed in the circulation

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3
Q

what is secretion?

A

the release of chemical substances to break down the food

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4
Q

how is motility related to digestion?

A

it involves the muscular activity which will propulse the food and allow for chemical breakdown and mixing of foods

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5
Q

what is the absorption aspect of digestion?

A

the transfer of nutrients into blood circulation

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6
Q

what is the role of GIT in homeostasis?

A

o Provide nutrients to the body which is needed for basic functions, regulation, growth & repair

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7
Q

what proportion of nutrients is absorbed by the GIT?

A

CHO 99%
FAT 95%
PROTEIN 92%

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8
Q

what properties of the GIT were observed in earth worms?

A

o Tubular nature

o Communication with the external environment at both ends

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9
Q

what is the length of the GIT in humans?

A

~4.5 m in adults

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10
Q

how much bigger is the GIT from the inside than the outside?

A

600x

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11
Q

what is the area covered by the GIT in adults?

A

200-250 m^2

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12
Q

what is the advantage of having such a large surface area in the GIT?

A

 Great increase in area allows to obtain the ability to absorb nutrients in such an efficient way

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13
Q

how is the wall of the GIT divided?

A

into 4 functional layers

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14
Q

what are the layers that compose the wall of the GIT?

A
  • serosa
  • muscularis externa
  • submucosa
  • mucosa
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15
Q

what layer of the GIT is identified as being “thin, but though layer of connective tissue which surround the entire tube?”

A

serosa

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16
Q

what layer is o Continuous with the messenter, holds the GIT in place?

A

serosa

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17
Q

what type of fibers is the musculais externa composed of?

A

longitudinal fibers (outer layer) and circular fibers (inner layer)

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18
Q

what happens when the outer layer of the muscularis externa contracts?

A

GIT shortens

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19
Q

what happens when the inner layer of the muscularis externa contracts?

A

lumen will narrow

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20
Q

what part of the GIT is formed by striated muscles?

A

Top 1/3 of esophagus, oral cavity, pharynx and anal sphincter

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21
Q

in what layer are the lymphatic and blood vessels found?

A

submucosa

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22
Q

what is the mucosa layer composed of?

A
  • muscularis mucosae
  • lamina propria
  • epithelial cells
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23
Q

what is muscularis mucosae?

A

smooth muscle

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24
Q

what is lamina propria?

A

loose connective tissue

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25
Q

what is the function of the epithelial cells?

A

secretory ; endocrine and exocrine gland

plays a role in absorption

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26
Q

does the ENS require input from the CNS?

A

NO

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27
Q

What is the ENS defined as?

A

• Independent, integrative nervous system

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28
Q

what is the main function of the ENS?

A 
activities of muscular and secretory and absorptive elements of the GIT such as
 o	Initiates
o	Programs
o	Regulates
o	Coordinates
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29
Q

what are the plexuses that form the GIT?

A

submucosal and myenteric plexus

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30
Q

what is a plexus?

A

collection of nerve cell bodies

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31
Q

where are sensory neurons receptors located?

A

receptors in mucosal/muscle layer

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32
Q

what do motor neurons in the ENS activate?

A

• Activate secretory cells, muscle cells and motor neurons (expand action of the neurons across the GIT wall)

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33
Q

although the plexuses are anatomically different in the ENS, do the function as one or multiple units?

A

function as a single unit

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34
Q

what does the myenteric plexus control?

A

smooth muscle

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35
Q

what does the submucosal plexus control?

A

controls glands of the endocrine cells

36
Q

excitatory enteric neurons act on which receptors?

A

muscarinic receptors

37
Q

what is released by excitatory enteric neurons?

A

ACh

38
Q

inhibitory enteric neurons act on which receptors?

A

NANC (non-adrenergic/non cholinergic)

39
Q

where do the sensory fibers in the cell bodies in plexuses receive information from?

A

they receive information from the gut chemo and mechanoreceptors

40
Q

how is the stimulus transformed into a response?

A

stimulus sent to receptors then to nerve plexus then to muscle cells or gland to produce a response

41
Q

what is the length of intra mural reflex

A

short

42
Q

what do parasympathetic neurons reach the wall of the GIT as?

A

preganglionic fibers

43
Q

what do preganglionic fibers synapse via?

A

• They synapse via nicotinic ACh receptors with enteric neurons

44
Q

what does it result in the system in parasympathetic neurons

A

o Increases excitation in the system

45
Q

what do sympathetic neurons reach the wall of the GIT as?

A

postganglionic fibers

46
Q

what do postganglionic fibers synapse via?

A

• Synapses via NA receptors with enteric neurons

47
Q

what effect is exerted by sympathetic neurons?

A

inhibitory effect thus causes vasoconstriction

48
Q

what reflexes are permitted by sensory neurons?

A

long reflexes

49
Q

give examples of some Non-GIT hormones?

A

o Growth hormones, thyroid hormones

50
Q

what may non-GIT hormones influence?

A

growth and development of the GIT

51
Q

can hormones be released by the GIT but influence activities outside of it?

A

yes, ex. grehlin increases appetide at the hypothalamic feeding center

52
Q

generally what do GIT hormones regulate?

A

activities within the GIT

53
Q

how does hormonal regulation of GIT actiity function?

A

diffusion of the endocrine system

54
Q

what is the largest and most diversified endocrine system of the body

A

GIT endocrine system

55
Q

how many hormones get released by the GIT?

A

~20-30

56
Q

what is a endocrine cell that releases a hormone that functions on itself?

A

Autocrine

57
Q

what is an endocrine cell that affects neighboring cells when releasing hormones?

A

paracrine cell

58
Q

what is the endocrine effect?

A

hormones release and enter the blood stream to get to other regions

59
Q

what type of hormones are the regulatory hormones of the GIT

A

Peptide hormones

60
Q

what are regulatory hormones of the GIT released from?

A

mucosa

61
Q

what is the pathway of the regulatory hormones of the GIT when released from the mucosa?

A

blood to liver to heart, through systemic circulation through out the body until they reach target cells

62
Q

what happens when a hormone interacts in a synergistical manner with a NT?

A

they potentiate one another

63
Q

what happens when a hormone interacts in a antagonistic manner with a NT?

A

they inhibit one another

64
Q

when talking about muscular activity of the GIT, what layers are involved?

A

2 muscle layers of the muscularis externa

65
Q

when referring to propulsion through the GIT; what does segmentation refer to?

A

rings of contraction causing for closing at different locations at different times

66
Q

what is persistalsis?

A

circular muscles where the ring of the muscles moves along the wall of the GIT

67
Q

how can the flow in the GIT be characterized?

A
  • slow
  • aboral
  • little to no resistance
68
Q

what is the other name given to the oral phase of swallowing?

A

volontary phase

69
Q

what is carried out by the oral phase of swallowing?

A

food is transported from anterior mouth to the pharynx

70
Q

what does swallowing involved?

A

Involves a series of reflexes coordinated in the deglutition center of the medulla oblongata via the cortex.

71
Q

where is the pharynx located?

A

back of the throat

72
Q

what senses the presence of the bolus in the pharyngeal phase?

A

sensory receptors

73
Q

in the pharyngeal phase. how does food move down?

A

-reflexes causes it to move down

74
Q

what happens when the bolus presses down on the epilottis?

A

reflexive contraction of the vocal cords and closure of the glottis and protect the lower airways

75
Q

what occurs when swallowing?

A

apnea

76
Q

what happes to the UES in the pharyngeal phase of swallowing?

A

it relaxes

77
Q

what are deglutition reflexes?

A

a series of protective reflexes is initasatied by stimulation of afferent fibers in the pharynx

78
Q

what signals the deglutition reflex?

A

the medulla

79
Q

what is controlled by the deglutition reflex?

A

o Protective functions
o Relaxation UES
o Deglutition apnea
o Contraction of the pharyngeal muscles

80
Q

what type of muscles composes the UES?

A

striated muscle

81
Q

what innervates the UES?

A

somatic- Vagus N (X)

82
Q

how is the UES when no food is present?

A

its contracted

83
Q

what NT is released to ensure closure of the UES?

A

ACh

84
Q

what is deglutition relaxation?

A

cessation of the impulse causes the muscle to relax

85
Q

what happens to ACh in the deglutition relaxation phase

A

decreases

PHGY 210 (11 decks)

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