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GI 2 Flashcards

1
Q

What is avoiding autodigesting

A

breaking food down into small enough molecules to be absorbed without digesting the cells of the GI tract

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2
Q

what are 3 challenges of digestive system

A

autodigestion, maintaining mass balance, defense

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3
Q

why is it hard to maintain mass balance

A

we secrete a lot more than we ingest (have to reabsorb most)

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4
Q

what is defense in the digestive system

A

absorbing water and nutrients while preventing bacteria, viruses and other pathogens from entering body

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5
Q

what are defense mechanisms

A

mucus, digestive enzymes, acid and lymphoid tissue

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6
Q

where are 80% of lymphocytes

A

in small intestine

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7
Q

how is water secreted

A

ions are transported from ECF into lumen
created osmotic gradient for water to follow

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8
Q

what secretes digestive enzymes

A
  1. exocrine glands (salivary and pancreas)
  2. epithelial cells in stomach and small int
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9
Q

how does secretion work in epithelial cells

A

proteins synthesized on rough ER and packaged in secretory vesicles until needed

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10
Q

what are mucus secretions

A

viscous glycoprotein (mucins) secretions that protect GI cells and lubricate the contents

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11
Q

what type of cell secretes mucus in stomach and salivary glands

A

mucus cells

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12
Q

what type of cell secretes mucus in intestines

A

goblet cells

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13
Q

what do most fluid secretions facilitate

A

digestion, soften and moisten

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14
Q

in stomach what kind of enzymes are there

A

enzymes preferring acidic conditions

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15
Q

in small intestine what kind of enzymes are there

A

enzymes preferring alkaline conditions

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16
Q

two purposes of motility

A
  1. moves food from mouth to anus
  2. mechanically mixing food breaks it into uniformly small particles
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17
Q

what part of digestive tract is skeletal muscle

A

mouth, pharynx, 1st part of esophagus

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18
Q

what is type of muscle is the digestive tract from 2nd part of esophagus on

A

smooth muscle

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19
Q

what is GI motility determined by

A

properties of smooth muscle and modified chemical/mechanical input from nerves, hormones, and paracrine signals

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20
Q

What type of smooth muscle cells are in digestive tract

A

single unit smooth muscle cells

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21
Q

what are single unit smooth muscle cells

A

gap junction slink them electrically and mechanically meaning uniform contraction

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22
Q

tonic smooth muscle that is usually contracted

A

sphincters
relaxes to allow material to pass

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23
Q

phasic smooth muscle that cycles between contraction and relaxation

A

2/3 esophagus, posterior region of stomach, small, large intestines

24
Q

what are slow waves

A

spontaneous depolarizations in GI smooth muscle

25
what are slow waves modified by
chemical input from neurons, hormones, and paracrine signals
26
where do slow waves originate
network of cells: interstitial cells of cajal (ICC) next to myenteric plexus
27
what are the ICC cells
modified smooth muscle cells serving as the pacemaker for slow wave activity
28
how does slow waves spread through the smooth muscle
gap junctions of adjacent smooth muscle
29
why does stomach have waves 3times/min but small int 12 times/min
different regions controlled by different ICC groups
30
what are 3 basic patterns of contraction occurring in the GI bringing different types of movement
1. migrating motor complex (motilin) 2. peristatic 3. segmental
31
when does migrating motor complex begin
between meals
32
where does migrating motor complex start
progressive wave of contraction begins in stomach and passes from section to section, terminating in ileum
33
what are the parts of the migrating motor complex
45-60 minutes quiescent 20-30 min of infrequent peristaltic contractions 5-15 mins cycle rapid forceful contractions
34
how long is MMC
90-120 mins
35
what does the MMC do
sweeps food remnants and bacteria out of the upper GI tract and into large intestine
36
what kind of movement are peristaltic contractions responsible for
forward movement (esophagus and less frequently in small int.)
37
what is peristaltic contractions
progressive wave of contraction of circular muscle behind a mass (bolus) of food (2-25cm/s)
38
what are segmental contractions responsible for
mixing (intestines)
39
what are segmental contractions
small segments alternatively contact and relax circular and longitudinal (churns and mixes)
40
what are the regulated functions in the GI system
motility and secretion
41
what forms the ENS
100-500 million neurons of submucosal and myenteric plexuses
42
what do neurons synapse with to regulate GI function
with eachother, smooth muscles, glands and epithelial cells
43
where are short reflexes integrated
originate in ENS and carried out entirely within wall of gut
44
where are long reflexes integrated
within CNS, some originate outside GI tract but some in ENS
45
what GI peptides alter motility and secretion to regulate GI function
hormones, neuropeptides, and cytokines
46
what similarities does the ENS share with CNS
- intrinsic neurons: within GI - neurotransmitters (many similar to CNS) and neuromodulators - glial support cells - diffusion barrier (blood gut barrier) - integrating center (can function autonomously)
47
what does myenteric plexus add input
motility
48
what does submucosal plexus add input
secretion from GI secretory cells
49
what stimuli causes short reflexes from ENS
distension, presence of food, osmolarity, acid
50
If a long reflex begins in brain what is it
cephalic reflex (feedforward and emotional)
51
what other type of info is sent to CNS
Sensory info ENS receives info from CNS via autonomic nerves
52
what does parasympathetic and sympathetic input do for digestion
parasympathetic enhances GI function (vagus) sympathetic inhibits
53
what can GI peptides act as
hormones or paracrine signals
54
what do GI peptides do
excite or inhibit motility and secretion
55
where are GI peptides secreted
secreted into lumen to act on apical membrane receptors or ECF to act on neighbouring cells - some act outside GI (brain)
56
how many peptides have been identified and how many are hormones
over 30 only a handful
57

Bmsc 208 (33 decks)

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