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PHYSIOLOGY GIS > lec 4 > Flashcards

lec 4 Flashcards

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1
Q

Anatomically the stomach is composed of

A

the fundus, body and the antrum.

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2
Q

Physiologically the stomach composed of

A

The orad portion or Gastric Reservoir part (tonic contraction):
2. the caudad portion or Antral pump (phasic contraction):

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3
Q

the caudad portion or Antral pump (phasic contraction):

A

lower third of the body & antrum

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4
Q

The orad portion or Gastric Reservoir part (tonic contraction)

A

fundus & upper two thirds of the body

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5
Q

The smooth muscle layers in the fundus and body are

A

thin

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6
Q

The smooth muscle layers in the antrum

A

has much heavier musculature

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7
Q

Control of gastric motility

A
  1. Vago-vagal reflex
  2. Parasympathetic and Gastrin
  3. Sympathetic
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8
Q

Vago-vagal reflex

A

fundal relaxation

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9
Q

Parasympathetic and Gastrin:

A

increase contraction force and frequency

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10
Q

Sympathetic

A

decrease contraction force and frequency

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11
Q

Function of Gastric Motility

A
  1. reservoir
  2. break food into small particles and mix food with gastric secretions
  3. empty gastric contents into the duodenum
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12
Q

volume when the stomach empty

A

50 ml;, 1 L ,1.5 L

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13
Q

The stomach AND V during meal

A

a 20-fold change in volume

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14
Q

The stomach AND tension during meal

A

little change in tension

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15
Q

The stomach AND intra-gastric pressure, during meal

A

little rise in intra-gastric pressure

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16
Q

cause of little change in tension and

little rise in intra-gastric pressure

A

deep folds of stomach

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17
Q

During a meal

A

the folds get smaller and nearly flatten out

the stomach relaxes slightly with each mouthful

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18
Q

three kinds of gastric relaxation difference

A

is the region and the receptors

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19
Q

Types of Receptors of gastric relaxation

A
  1. receptive relaxation
  2. adaptive relaxation
  3. feedback-relaxation
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20
Q

receptive relaxation

A

swallowing of food (before stomach )

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21
Q

adaptive relaxation

A

food in stomach →stretch receptors

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22
Q

feedback-relaxation

A

food in duodenum →the release of CCK

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23
Q

stretch receptors

A

mechano or tension receptors)in stomach

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24
Q

;givegus

A

Afferent: vagus

c. Center: vagal center
d. Efferent: vagus ►enteric neurons (inhibitoryneurotransmitter: Nitric oxide or VIP)
e. Effector organ: muscle relaxation of stomach wall

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25
vagal innervation is interrupted
↑ intra-gastric pressure →vomiting
26
vomiting result from
the inability of the proximal stomach smooth muscle to undergo receptive relaxation.
27
the newest food lying closest to
the esophageal opening
28
the oldest food lying nearest the
the outer wall of the stomach
29
functions of gastric reservoir
to store | to evacuate digesta
30
The emptying of the reservoir is caused by two mechanisms:
by a tonic contraction of the reservoir and | by peristaltic waves moving
31
As food enters the stomach, it forms
the food in the orad portion of the stomach
32
Both the peristaltic waves and the tonic | contractions of the reservoir are stimulated
by cholinergic & enteric neurons
33
cholinergic & enteric neurons are | under modulatory
vagal tone
34
In the region of the gastric corpus the | peristaltic waves only produce
a small circular constriction → mix superficial layer
35
in the center of the gastric reservoir
the pH remains high and the digestion of starch by amylase continues
36
Mechanical contraction of stomach
Electrical activity of gastric wall | Mixing movement:
37
Peristaltic activity, manifested as
slow waves occurs at the basal electrical rate (BER) of the stomach (3-4 waves/minute)
38
Slow waves conducted through
gap junctions along longitudinal muscle layer
39
زس ما هي
in the mid-portion of the greater curvature (the proximal corpus), and travel distally towards the pylorus once every 15 to 20 seconds Propagating is slightly faster velocity along the greater curve than along the lesser curve.
40
The gastric action potential lasts about
5 seconds
41
four phases of A,P IN GI
0و1و4و3و
42
Phase 0
Resting membrane potential; outward potassium current.
43
Phase 1
``` Rising phase (upstroke depolarization); activation of voltage-gated calcium channels and voltage-gated potassium channels. ```
44
Phase 3
Plateau phase; balance of inward calcium current and outward potassium current
45
Phase 4
``` Falling phase (repolarization); inactivation of voltage-gated calcium channels and activation of calcium-gated potassium channel ```
46
Mixing movement includes
1. Peristaltic movements | 2. Retropulsion movements
47
The mechanical peristaltic movements caused by
depolarizing spikes at peak of basal electrical rhythm cycle
48
peristaltic contraction increases by
``` Gastric distension ↓ vagal stimulation ↓ release of acetylcholine ↓ increase of gastrin ↓ ↑contraction ```
49
Peristaltic contraction begins in
the mid stomach and proceed caudally.
50
As the wave proceeds towards the pylorus it become
deeper, stronger and faster (
51
in pylorus traveling
3-4 cm/sec
52
in fundus
(< 1 cm/sec) .
53
n the deep wave of contraction
at proximal third of antrum away from pylorus:
54
pylorus is relaxed
peristalsis may push antral content (water and small food particles) toward the duodenum
55
Pylorus thickness of the circular wall muscle becomes
50 to 100 percent | greater than in the earlier portions of the stomach antrum
56
the pyloric circular muscle is called
the pyloric sphincter.
57
why the pyloric circular muscle is called the pyloric sphincter.
Pylorus remains slightly tonically contracted almost all the time
58
solids food fate
1. reduced to between 1-2mm in size before delivered to the duodenum. 2. large, indigestible solids remain in the stomach
59
Retropulsion movements
sievingغربلة function
60
antral systole)
peristaltic waves are most marked in distal half of stomach
61
Liquids pass through the pylorus in
spurtsدفقات
62
In the fasting condition the pyloric sphincter remains
relaxed
63
When food enters the pyloric sphincter re
closes
64
The time of opening the sphincter depends on:
a) The normal motility of the stomach, (b) Quality and consistency of the food (c) Stage of digestion
65
with water and liquid diet, the sphincter
opens
66
a mixed diet the sphincter opening starts
15 minutes (average half an hour)
67
The degree of constriction of the pylorus is increased or decreased under the influence of
nervous signals hormonal signals from both the stomach and the duodenum Some evidence suggests that it is controlled by opiates, acetylcholine, and nitric oxide (NO)
68
retropulsion
The backward movement of food particles
69
mixing movement beneficial effects are
to effectively mix food and gastric secretions, | to grind gastric contents into chyme.
70
Gastric emptying is
the chyme is expelled from the stomach into the duodenum
71
Gastric emptying results from a
progressive wave of forceful contraction
72
Gastric emptying involves
antrum pyloric sphincter proximal duodenum
73
Gastric emptying is determined by the force of
gastric peristalsis and NOT the variation in tone of pyloric sphincter
74
Gastric emptying waves
spread over the antrum as strong peristaltic ring-like contraction
75
Gastric emptying waves
50-70cmH2O
76
Gastric emptying occurs when the chyme is decomposed into
enough small pieces | (typically <1 mm2) to fit through pyloric sphincter.
77
Significance of gastric emptying:
1.prevents solid and bigger food particles from entering التحكم ب حجم حبات الطعام duodenum 2.allows small volume (2-7mL) of chyme from entering التحكم ب حجم سائل الطعام.time a at duodenum 3.prevents التحكم ب عدم رجوع الطعامstomach in chyme of regurgitation
78
The contraction of the pyloric (or gastric or antral ) pump phases
phase of propulsion phase of emptying phase of retropulsion and grinding
79
phase of retropulsion and grinding
terminal antrum  Jet-like back-flow with grinding + duodenal contraction Retropulsion of large particles and clearing of the terminal antrum Due to the regularly occurring pacesetter potentials these phases occur cyclically.
80
phase of propulsion
Contraction of proximal antrum Propulsion of chyme into terminal antrum + Duodenal contraction Raid flow of liquids with suspended small particles and Delayed flow of large particles towards pylorus
81
phase of emptying
Contraction of middle antrum Transpyloric and retrograde flow +  duodenal relaxation Emptying of liquids with small particles whereas large particles are retained in the bulge of the terminal antrum

PHYSIOLOGY GIS (17 decks)

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