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PHYSIOLOGY GIS > lec 4 > Flashcards

lec 4 Flashcards

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
Q

vagal innervation is interrupted

A

↑ intra-gastric pressure →vomiting

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26
Q

vomiting result from

A

the inability of the proximal stomach smooth muscle to undergo receptive relaxation.

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27
Q

the newest food lying closest to

A

the esophageal opening

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28
Q

the oldest food lying nearest the

A

the outer wall of the stomach

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29
Q

functions of gastric reservoir

A

to store

to evacuate digesta

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30
Q

The emptying of the reservoir is caused by two mechanisms:

A

by a tonic contraction of the reservoir and

by peristaltic waves moving

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31
Q

As food enters the stomach, it forms

A

the food in the orad portion of the stomach

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32
Q

Both the peristaltic waves and the tonic

contractions of the reservoir are stimulated

A

by cholinergic & enteric neurons

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33
Q

cholinergic & enteric neurons are

under modulatory

A

vagal tone

34
Q

In the region of the gastric corpus the

peristaltic waves only produce

A

a small circular constriction → mix superficial layer

35
Q

in the center of the gastric reservoir

A

the pH remains high and the digestion of starch by amylase continues

36
Q

Mechanical contraction of stomach

A

Electrical activity of gastric wall

Mixing movement:

37
Q

Peristaltic activity, manifested as

A

slow waves occurs at the basal electrical rate (BER) of the stomach (3-4 waves/minute)

38
Q

Slow waves conducted through

A

gap junctions along longitudinal muscle layer

39
Q

زس ما هي

A

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
Q

The gastric action potential lasts about

A

5 seconds

41
Q

four phases of A,P IN GI

A

0و1و4و3و

42
Q

Phase 0

A

Resting membrane potential; outward potassium current.

43
Q

Phase 1

A 
Rising phase (upstroke depolarization); activation of voltage-gated calcium 
channels and voltage-gated potassium channels.
44
Q

Phase 3

A

Plateau phase; balance of inward calcium current and outward potassium current

45
Q

Phase 4

A 
Falling phase (repolarization); inactivation of voltage-gated calcium channels and 
activation of calcium-gated potassium channel
46
Q

Mixing movement includes

A
  1. Peristaltic movements

2. Retropulsion movements

47
Q

The mechanical peristaltic movements caused by

A

depolarizing spikes at peak of basal electrical rhythm cycle

48
Q

peristaltic contraction increases by

A 
Gastric distension 
↓
vagal stimulation 
↓
release of acetylcholine 
↓
increase of gastrin 
↓
↑contraction
49
Q

Peristaltic contraction begins in

A

the mid stomach and proceed caudally.

50
Q

As the wave proceeds towards the pylorus it become

A

deeper,
stronger and
faster (

51
Q

in pylorus traveling

A

3-4 cm/sec

52
Q

in fundus

A

(< 1 cm/sec) .

53
Q

n the deep wave of contraction

A

at proximal third of antrum away from pylorus:

54
Q

pylorus is relaxed

A

peristalsis may push antral content (water and small food particles) toward the duodenum

55
Q

Pylorus thickness of the circular wall muscle becomes

A

50 to 100 percent

greater than in the earlier portions of the stomach antrum

56
Q

the pyloric circular muscle is called

A

the pyloric sphincter.

57
Q

why the pyloric circular muscle is called the pyloric sphincter.

A

Pylorus remains slightly tonically contracted almost all the time

58
Q

solids food fate

A
  1. reduced to between 1-2mm in size before delivered to the duodenum.
  2. large, indigestible solids remain in the stomach
59
Q

Retropulsion movements

A

sievingغربلة function

60
Q

antral systole)

A

peristaltic waves are most marked in distal half of stomach

61
Q

Liquids pass through the pylorus in

A

spurtsدفقات

62
Q

In the fasting condition the pyloric sphincter remains

A

relaxed

63
Q

When food enters the pyloric sphincter re

A

closes

64
Q

The time of opening the sphincter depends on:

A

a) The normal motility of the stomach,
(b) Quality and consistency of the food

(c) Stage of digestion

65
Q

with water and liquid diet, the sphincter

A

opens

66
Q

a mixed diet the sphincter opening starts

A

15 minutes (average half an hour)

67
Q

The degree of constriction of the pylorus is increased or decreased under the influence of

A

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
Q

retropulsion

A

The backward movement of food particles

69
Q

mixing movement beneficial effects are

A

to effectively mix food and gastric secretions,

to grind gastric contents into chyme.

70
Q

Gastric emptying is

A

the chyme is expelled from the stomach into the duodenum

71
Q

Gastric emptying results from a

A

progressive wave of forceful contraction

72
Q

Gastric emptying involves

A

antrum
pyloric sphincter
proximal duodenum

73
Q

Gastric emptying is determined by the force of

A

gastric peristalsis and NOT the variation in tone of pyloric sphincter

74
Q

Gastric emptying waves

A

spread over the antrum as strong peristaltic ring-like contraction

75
Q

Gastric emptying waves

A

50-70cmH2O

76
Q

Gastric emptying occurs when the chyme is decomposed into

A

enough small pieces

(typically <1 mm2) to fit through pyloric sphincter.

77
Q

Significance of gastric emptying:

A

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
Q

The contraction of the pyloric (or gastric or antral ) pump phases

A

phase of propulsion
phase of emptying
phase of retropulsion and grinding

79
Q

phase of retropulsion and grinding

A

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
Q

phase of propulsion

A

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
Q

phase of emptying

A

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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