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b. phys exam 2 (w13) > 2/12-GI tract > Flashcards

2/12-GI tract Flashcards

1
Q

what type cells make up most of the GI tract (stomach to sigmoid colon)

A

simpe columnar epithelium

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2
Q

how long is mouth to anus?

A

10 arm lengths

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3
Q
  1. what kind of epithelium is in the mouth, esophagus and anus?
  2. what kind is in the rest of the Gi tract?
A
  1. stratified squamous

2. simple columnar

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3
Q
  1. how does the GI tract keep oxygen from being lost into the lumen from the circulatory system?
  2. how much oxygen is retained?
A
  1. the GI tract uses a countercurrent system where the oxygen jumps from the arterial system to the venous system which is parallel
  2. 80% of oxygen is retained
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4
Q

what are lacteals?

A

tit looking lymphatics ducts that run up through each villi

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5
Q

what is the mucosa muscularis?

A

a very thin layer of smooth muscle which forms the border between the mucosa and the submucosa.

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6
Q

what is the submucosal plexus (what does it do)?

A

it is a nerve plexus in the GI tract which contains:

a) taste buds
- for bitter: (alkyloids/ endo-toxins)
- for acidic: (rotten)
b) regulates blood flow
c) regulates glands
d) moves musculature (mucoa muscularis)

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8
Q

what are the 4 layers of the GI tract?

A
  1. mucosa
  2. submucosa
  3. muscularis externa
  4. adventitia or serosa
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9
Q

what lies between the mucosa and submucosa?

A

mucosae muscularis- a thin layer of smooth muscle

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10
Q
  1. what is the submucosa?

2. what is contained in it? (2 things)

A
  1. the second layer of the GI tract
  2. contains:
    a) glands that secrete bicarb and mucous into the lumen
    b) submucosal plexus
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11
Q

what does the mesenteric plexus do/contain?

A

a) contains reflex arcs for the brain, spine and other parts of GI to communicate with
b) ganglion from parasympathetic (vagus via medulla) target the mesenteric plexus,
c) motor innervation to both layers of muscularis externa, controls gastric motility.
d) contains sympathetic and parasympathetic inputs

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12
Q

muscularis:

what types of muscle, how many layers & what does each one do?

A
  1. circular: the innermost muscle layer- responsible for preventing regurg of food backward into GI tract by squeezing down behind the chyme bolus and dilating in front of it.
  2. mesenteric plexus- sits between two muscle layers; is the target organ for parasympathetic innervation; contains reflex arcs from brain and spine that tell bowels to make room for new food, regulates movement thru interstitial cells of Cajal
  3. longitudinal: outermost muscle layer- shortens the GI tract
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13
Q
  1. The stomach is unique, how many muscle layers does the STOMACH have?
  2. what are they?
  3. what does the last layer do?
A 
1. three
2 a)circular
b) longitudinal
c) oblique 
3. Oblique physcially digests food by churning
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14
Q
  1. what is the 4th layer of the GI tract?
  2. what does it do?
  3. why dont we feel this?
A
  1. serosa
  2. a part of the mesentary of the visceral peritonium (the wrapping); it secretes serous fluid that allows bowels to slosh back and forth (preventing torsion of the bowel)
  3. there are no proprioceptors in the bowels
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15
Q

smooth muscle contractions:

  1. what is the resting wave called? what causes it (2 possibilities)?
  2. what happens when there is increase parasympathetic signaling?
  3. what happens when there is sympathetic signaling?
  4. what nerves send the sympathetic message?
A
  1. slow wave potentials (just a slight up and down movement of action potentials at the resting potential
    - -caused by wax and wane of Na+/K+ channels or leak channels that stay open for a short time then close for a short time).
  2. parasympathetic signals cause the GI to reach threshold with spikes of action potentials above threshold causing movement
  3. sympathetic signals cause the cells to hyperpolarize below the resting potential (very slight low waves)
  4. sympathetic signals come from the prevertabral ganglia (ciliac, mesemteric, hypogastric).
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16
Q

where does parasympathetic innervation for bowel come from?

A
  1. vagus nerve controls upper GI

2. sacral plexus (s2, s3, s4) controls lower GI

17
Q

where does sympathetic innervation for bowel come from?

A

thoracic prevertebral ganglion (T5-L2), which make up the ciliac, mesenteric and hypogastric nerves.

18
Q
  1. what type of smooth muscle is GI muscle?

2. how does it work?

A
  1. unitary smooth muscle
  2. a nerve terminis runs along side the cells, the terminis secretes Ach to the cells
    pacemaker cell of cajal starts an action potential that runs thru gap junctions causing the whole cell group to become active
19
Q
  1. where does smooth muscle get its calcium?

2. what does calcium do to cause muscle contractions?

A
  1. all from extracellular sourcs
  2. a) calcium binds to calmodulin causing myosin and kinase to add P++ to myosin to form (- charged)MYOSIN PHOSPHATE.
    b) myosin phsophate will then latch to cause contraction
    c) when myosin phosphate is done, the phosphate molecule leaves and it becomes (+ charged) myosin kinase again
20
Q

how is peristalsis accomplished?

A
  1. food bolus pushes on lumen
  2. mesenteric plexus senses stretch and sends message downstream to relax
  3. pressure decreases and bolus moves to path of least resistance
  4. scenario repeats
21
Q

what is the differece between antegrade axons (going torward anus) and retrograde axons (going backward)?

A

antegrade axons are shorter than retrograde axons

22
Q

what is segmentation?

A

the sloshing back and forth of chyme between 2 segments of bowel. this breaks the chyme into “di”’s and “tri”’s (dipeptides and triglycerols).

23
Q

immune system of GI tract

  1. how does the lymph system work?
  2. what is in the walls of he GI tract and what does it do?
A
  1. you dont have lymph nodes, you have lacteals (which look like cow tits).
  2. you have peyers patches in the walls of the GI tract. via diapedesis, some of the macrophage will go into the gastric tract and “taste” the contents and present antigens to the immune system.
24
Q

neuronal level:

  1. what reflex arcs are part of the neuronal system?
  2. what digestive centers are in the brain?
  3. where is cell body for vagus at?
  4. what is the communication between sensory and motor vagus called?
  5. where do the pain sensors for the abdomen originate?
  6. what does vagus do to slow wave height?
  7. what does pre-vertebral ganglion do to slow wave height?
  8. what does the enteric plexus sense?
A
  1. reflex arcs (gastrocolic, enterogastric & coloileac)
  2. brain has centers for salivation, chewing etc.
  3. cell body for vagus is in brainstem
  4. vagus-vagus response (80% of vagus is sensory)
  5. dermatomes sense pain in prevertebral ganglion
  6. vagus sends to increase slow wave height
  7. pre-vertebral ganglion decreases slow wave height
  8. stretch and pain
25
Q

hormonal level:

  1. what is the hormone that senses fatty acids? what does it do? where is it produced? what else does does it do?
  2. what is the hormone that senses H+ ions (acid)? what does it do? where is it released from? what else does it do?
  3. what hormone senses fatty acids and amino acids? what does it do? where is it released from?
A

1-CCK (CHOLECYSTOKININ) gets released into blood by “I” cells (in columnar epithelium of duodenum) in the presence of fatty acids (this prevents the stomach from releasing more food until it can be emulsified and causes contraction of gall bladder to release more bile)
2-SECRETIN: gets released from “S” cells found in columnar cells in duodenum epithelium in presence of acid (H+ ions); tells the stomach to stop releasing food and tells pancrease tosecrete more bicarb.
3-GIP (GASTRIS INHIBITORY PEPTIDE): slows stomach in presence of amino acids and fatty acids. cell that it is produced from is unknown.

26
Q

what is motillin?

A

a hormone secreted when fasting, causes bubbles to rumble over rugae of stomach (stomach growls).

27
Q

what is the gastrocolic reflex arc

A

stomach stretches in am from breakfast and causes a big push to make you deficate

28
Q

what is the entero-gastric reflex arc

A

duodenum becomes distended from too much chyme being dumped by stomach- sends message to stomach to stop

29
Q

what is the coloileac reflex arc?

A

colon tells ileum to stop sending feces down because it is too distended

b. phys exam 2 (w13) (6 decks)

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