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PHGY 210 > digestion - lecture 3 > Flashcards

digestion - lecture 3 Flashcards

1
Q

describe upper git pressures

A

pharynx = continuous with mouth at atm
ues = very positive
body of eso = intrathoracic - so neg -5mmhg, so if not closed then contents of stomach will be sucked into eso and air from mouth
les = positive but way less then ues
intragastric pressure = slight positive

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2
Q

name and describe
2 esophageal forces

A

gravity = minor importance- small effect for liquid
peristalsis = esophageal contents carried towards stomach = most of force

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3
Q

what is peristalsis

A

wave of contraction moving over wall of organ
narrows lumen
sets up gradient of pressure favoring aboral movement

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4
Q

describe peristalsis

A

each time we swallow = one single primary peristaltic wave generated
takes 8-10 seconds to be propagated length of eso

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5
Q

what is primary peristalsis part of

A

deglutition reflexes

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6
Q

describe deglutition center - somatic and autonomic

A

driven by diff inputs depending on if started or smooth muscle
sends vagus somatic (striated) and autonomic (smooth) fibers
both excitatory = activates ens - not directly on muscle then ens activates muscle

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7
Q

describe deglutition center - somatic

A

Sequential proximal to distal wave of activity of striated muscle
smooth wave
activated based on location first

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8
Q

describe deglutition center - autonomic

A

synchronous activation
increased latency of activation in distal eso
wave of activity in smooth muscle
each activates = slightly longer than others = gradient

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9
Q

what is latency

A

time between onset of stimulation and response

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10
Q

describe musculature of esophagus

A

proximal third of eso striated
distal third smooth
peristaltic wave moves over entire eso as smoothly propagated wave

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11
Q

describe musculature of esophagus - striated portion

A

peristalsis results from sequential firing of vagal motor neurons
activating progressively more distal regions of musculature

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12
Q

describe musculature of esophagus - smooth muscle portion

A

once some of enteric neurons have been activated = capable of relaying and activating other enteric neurons = orderly fashion
evokes and propagtes muscular contraction in aboral direction - independent of extrinsic nerves
integrity of enteric innervation critical to propagation of peristaltic wave in distal esophagus

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13
Q

what happens when cut vagal nerve - high up

A

high up in neck = no primary peristalsis

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14
Q

what happens when cut vagal nerve - lower down

A

cut transthoracically = primary peristalsis continues
since propagates through ens and leads to contraction of next spot too
need one autonomic fiber intact
distal eso has enteric circuitry needed for propagation of peristaltic wave

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15
Q

what regulates primary peristalsis

A

vagus nerve = essential for imitating peristalsis in proximal eso
intact ens = essential for continuing and propagating peristalsis in distal eso
vagal somatic = skeletal muscle of upper eso
vagal autonomic = ens of lower eso
wave of contraction

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16
Q

what happens when bolus gets stuck in eso

A

secondary peristalsis

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17
Q

describe secondary peristalsis

A

Initiated by local distension
mediated by enteric reflexes (short, local) or long reflexes
(vagal sensory afferents to cns = reinforce efferent vagal input = VAGAL-VAGAL reflexes)
activates ens
several secondary peristaltic waves must be generated until bolus displaced

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18
Q

describe les - anatomically

A

terminal 4 cm of eso = smooth muscle
thickening of muscle of sphincter (no visible enlargement of circular muscles) NOT SEEN IN LES
half above - 2cm and half below - 2cm diaphragm

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19
Q

describe les - ability and function

A

Anatomically insignificant = property of muscle itself
ability to act as sphincter is property of musculature
has residual resistance in absence of ens or autonomic innervation
functionally important
constant tone = no input from cns

20
Q

describe les closure and relaxation

A

closure is myogenic = contracted at rest
relaxation is neurogenic = local ens release of NACN (-) or v agal stimulation to activate inhibitory ens neurons
comes from deglutition center = excitatory inputs (parasymp) activates inhibitory ens neurons

21
Q

is les relaxation part of deglutition reflexes

A

YES YOU KNOW IT IS LOSER

22
Q

describe les - definition

A

lowest 4 cm of eso
straddles diaphragm
in absence of swallowing sphincter in state of tone = walls in firm apposition
les tone is myogenic but can subject to neural and hormonal influences

23
Q

describe relaxation of les - generally

A

Reflex
Initiated during swallowing
mediated by vagal efferent fibers releasing ach = activate inhibitory enteric neurons which release nanc transmitters = causes decreased muscle tone

24
Q

describe normal les

A

2cm above diaphragm and 2 cm below
thoracic cavity = -5mmhg
abdominal cavity = +5mmhg
intragastric pressure of les = 20mmhg
Increases when bend over or pregnant

25
Q

describe what happens if intraabdominal pressure increases

A

increases pressure equally on stomach and intraabdominal les

26
Q

describe les if 100mmhg increase

A

pressure now = 120mmhg = preserves barrier
Thoracic = -5mmhg
abdominal = 105mmhg

27
Q

describe hiatus hernia

A

if les displaced into thorax = intraabdominal pressure increases and does not increase les pressure
all pushed above = wont prevent flow of contents now

28
Q

describe les - segments

A

intrathoracic segment - subject to neg pressure
intraabdominal segment - subject to positive pressure = allows sphincter to maintain effective barrier
pressures within these segments vary with phases of respiration
intraabdominal pressure raised = pressure in terminal segment of les and intragastric compartment raised equally
so that there is no effective change in gradient of pressure between stomach and eso

29
Q

describe 2 characteristics of les

A

1 = intrinsic - property of thing itself - physiological sphincter = tonically contracted in absence of swallowing
2 = anti reflux mechanism assisted by presence of an intraabdominal segment

30
Q

what happens of incompetent les

A

sphincter fails to close

31
Q

what is pyrosis

A

heart burn
burning sensation
radiates upwards in chest towards neck
due to acid reflux into esophagus
eso cannot protect itsself from stomach acids

32
Q

describe progesterone effect on les

A

lowers resistance in les
many women in last trimester = have heartburn
also increase pressure intraabdominal since have fetus in abdomen

33
Q

describe gastrin effect on les

A

if increase = closes les
gastrin also increases acidity
does not effect at physiological levels of gastrin = have to be hella high

34
Q

name and describe the 3 motor functions of stomach

A

1 - temporary storage = 1-2L of food/drink
2 - physical disruption and mixing of contents = bolus –> semi liquid consistency = chyme
3 - propulsion into duodenum= regulated propulsion = need to give time for si to absorb

35
Q

describe stomach anatomically

A

parts = fundus, body, antrum, pylorus
proximal = storage, thin walled, relaxation of upper part to accommodate meal
distal = mixing and propulsion, thick walled, need strong muscle

36
Q

describe stomach wall

A

same 4 basic layers as rest of git but some modifications

37
Q

describe gastric mucosa

A

folds called rugae
many diff cell types = arranged in pits and glands, all epithelial in origin

38
Q

describe musculares externa of stomach

A

contains extra layer of sm
= oblique muscle
grinding - movement of stomach

39
Q

what is intragastric pressure

A

empty stomach has small vol = 50ml
pressure inside increases greatly if put much food in it

40
Q

how does stomach accommodate the meal

A

receptive relaxation
increase in vol without significant increase in intraluminal pressure
restricted to proximal stomach
too high of pressure = contents move into si more rapidly
expands capacity

41
Q

what is receptive relaxation

A

ens inhibitory neurons - local
Excitatory vagel efferents activate ens inhibitory neurons
leads to relaxation of musculature in proximal stomach
larger and less pressure
happens before meal arrives

42
Q

is receptive relaxation a deglutition reflex

A

yes

43
Q

describe vago vagal reflex in stomach

A

most of stretch happens when meal arrives
need more relaxation
vagal afferents sense distension and leads to vagal vagal feedback
Further activates inhibitory neurons
need before meal, ens, and vagal vagal to stretch stomach

44
Q

what happens if vagi to proximal stomach cut

A

receptive relaxation limited = great increase in intragastric pressure

45
Q

describe whole phases of deglutition - summary

A

reflexes controlled in deglutition center
oral–>pharnygeal–>esophageal–>gastric
with intake of meal and stimulation of deglutition center= have a wave of activation and relaxation that carries bolus along upper git and allows it to be accomodated in stomach

PHGY 210 (36 decks)

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