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Gastrointestinal Case > Motility in the GI Tract > Flashcards

Motility in the GI Tract Flashcards

1
Q

What are the main functions of the motor activity of the GI tract

A

Non-propulsive movements (segmentation)
Peristaltic movements
Reservoir function

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2
Q

What are two types of muscularis externa contractions

A

Phasic

Tonic

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3
Q

What’s the time scale for phasic muscle contractions ?

A

Seconds

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4
Q

What’s the time scale for tonic muscle contractions ?

A

Minutes- hours

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5
Q

What are non-propulsive movements (segmentation)

A

churn up contents of the GI tract to promote digestion and absorption

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6
Q

What are peristaltic movements

A

process of moving material along the gastrointestinal tract

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7
Q

What is the reservoir function

A

isolating different section of the GI tract for storage

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8
Q

How is the reservoir function performed

A

by sphincter

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9
Q

Give examples of sphincters and what they are reservoirs for?

A

Stomach- after meal

Large Intestine- waste

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10
Q

What of the motor activity of the GI tract functions are phasic contractions

A

Non-propulsive movements (segmentation)

Peristaltic movements

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11
Q

What of the motor activity of the GI tract functions are tonic contractions

A

Reservoir function

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12
Q

What type of contraction does the Non-propulsive movements (segmentation) carry out

A

Phasic

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13
Q

What type of contraction does the Peristaltic movements carry out

A

Phasic

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14
Q

What type of contraction does the reservoir function carry out

A

Tonic

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15
Q

What type of muscle is the muscularis externa 1/3 of the way of the oesophagus to the rectum

A

Smooth muscle

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16
Q

What type of muscle is the muscularis externa in the upper 1/3 of the oesophagus

A

skeletal muscle

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17
Q

When is the muscularis externa smooth muscle

A

1/3 of the way of the oesophagus to the rectum

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18
Q

When is the muscularis externa skeletal muscle

A

upper 1/3 of the oesophagus

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19
Q

What is a single muscular unit?

A

Muscle fibres act together as a functional unit

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20
Q

How is the smooth muscle of the muscularis externa organised? How is this beneficial?

A

Two smooth muscle cells connected to three varicosities connecting the nerve to the smooth muscle fibre
So that there is signalling from the nerve to the smooth muscle cell
Innovated smooth muscle cells connected to other muscle cells to other smooth muscle cells by gap junctions
coordinated activity of the muscle fibres

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21
Q

What is a special feature of the membrane voltage within the smooth muscle cells of the muscularis externa of the GI tract

A

Slow waves
Oscillations of the membrane voltage within the smooth muscle cells of the muscularis externa of the GI tract
When action potential fired membrane becomes very negative
reaches a hyperpolarisation threshold
starts to make it positive but doesn’t reach action potential threshold
becomes more positive again after modulation where it reaches action potential
Action potential fires again
Slower than skeletal muscle action potential

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22
Q

What is the resting potential of the muscularis externa of the GI tract

A

Depolarised ( -40 ~ -60mV)

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23
Q

How is slow waves within the smooth muscle cells of the muscularis externa of the GI tract modulated

A 
Hormones and nerves
e.g 
Acetycoline
Cholecystokinin
Make waves more positive to reach action potential threshold
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24
Q

How is the frequency of muscle contractions dictated?

A

Frequency of action potential firing which is determined by slow waves

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25
Q

What are sphincters

A

Specialised builging of the inner circular muscles from the muscularis externa

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26
Q

What do sphincters do?

A

separate two adjacent compartments of the GI tract
Maintain positive resting pressure
Regulate antegrade and retrograde movement
Effectively serve as one-way valves

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27
Q

What does antegrade mean

A

Forward moving

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28
Q

What does retrograde mean

A

Backward moving

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29
Q

What are the sphincters ogf the GI tract

A 
Upper oesophageal sphincter (UES)
Lower oesophageal sphincter (LES)
Pyloric sphincter
Sphincter of Oddi
Ileocecal sphincter
Internal and external anal sphincters
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30
Q

Where is the Upper oesophageal sphincter (UES) located?

A

The top of the oesophagus

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31
Q

Where is the Lower oesophageal sphincter (LES) located?

A

At the bottom of the oesophagus

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32
Q

Where is the Pyloric sphincter located?

A

At the bottom of the stomach

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33
Q

Where is the Ileocecal sphincter located?

A

At the bottom of the small

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34
Q

Where is the Internal and external anal sphincters located?

A

At the rectum

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35
Q

How is the stomach isolated as a reservoir?

A

By the action of the Pyloric sphincter at the bottom and Lower oesophageal sphincter (LES) at the top

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36
Q

How is the action of the pyloric sphincter important

A

Regulating release of partially digested food from the stomach into the small intestine after a meal

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37
Q

How is the small intestine isolated as a reservoir?

A

By the action of the Pyloric sphincter at the top and Lower oesophageal sphincter (LES)

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38
Q

How is the small intestine isolated as a reservoir?

A

By the action of the Pyloric sphincter at the top and ileocecal sphincter at the bottom

39
Q

How is the large intestine isolated as a reservoir?

A

By the action of the internal and external anal sphincter at the bottom and ileocecal sphincter at the top

40
Q

Which sphincter is made of skeletal muscle and why is this important

A

External anal sphincter
As for voluntary movement
so don’t automatically discharge. Go to the toilet

41
Q

Where is the Sphincter of Oddi located

A

Wrapped around two ducts coming into the dduodenum:

    • Pancreatic
  • biliary/ bile
42
Q

What is the contraction of Sphincter of Oddi role

A

regulating delivery of pancreatic juice and bile from biliary system into duodenium

43
Q

What is the epithelium of the oesophagus and why?

A

Stratified squamous epithelium

Protective mechanism from acid reflux from stomach

44
Q

What are the type of sphincters are sphincters normally?

A

Anatomical

45
Q

Which type of sphincter is the lower oesophageal sphincter

A

Physiological

46
Q

What is the difference between an Anatomical and physiological sphincter?

A

Anatomically - bulging of the inner circular muscular layer

Physiological- no bulging but different in physiology

47
Q

How is closure of the lower oesophageal sphincter achieved?

A

Contraction of the diaphragm
intra-abdominal pressure is greater than the intra- gastric pressure
anatomical organization of the gastrointestinal tract

48
Q

What movement is more common in the GI tract antegrade or retrograde

A

Antergrade

49
Q

How are the contraction of the sphincters cordinated?

A

smooth muscle contractions of adjacent compartments

50
Q

What of the GI reflexes are voluntary

A

Swallowing reflex

51
Q

Process of swallowing

A

Initiated voluntarily
then entirely under reflex control
tongue is gonna push a bolus of food to the back of the mouth
In the pharynx that bolus of food is going to activate touch receptor
Touch receptors communicate with medulla and lower pons
By cranial nerves swallowing reflex is going to control the pharynx and the upper oesophagus
By vagal nerves the rest of the oesophagus

52
Q

What is a bolus of food

A

Food mixed with saliva

53
Q

Where is the bolus of food is going to activate touch receptor

A

In the pharynx

54
Q

When in the swallowing reflex does the reflex become involuntary

A

When medulla and pons is activated

55
Q

Swallowing reflex- Once medulla and lower pons activated what controls the pharynx and upper oesophagus

A

cranial nerves

56
Q

Swallowing reflex- Once medulla and lower pons activated what is controlled by the cranial nerves

A

pharynx and upper oesophagus

57
Q

Swallowing reflex- Once medulla and lower pons activated what is controlled by the vagal nerves

A

Th rest of the oesophagus that is not the upper oesophagus

58
Q

Swallowing reflex- Once medulla and lower pons activated what controls the rest of the oesophagus that is not the upper oesophagus

A

Vagal nerves

59
Q

What are the three phases of swallowing

A

Oral phase/ Voluntary phase
Pharyngeal phase
Oesophageal phase

60
Q

Process of swallowing: Oral phase/ Voluntary phase

A

The tongue presses the food against the hard palate
The bolus is forced into the pharynx and stimulates touch receptors
Signal to medulla and pons

61
Q

Process of swallowing: Pharyngeal phase

A

soft palate elevates
epiglottis closes trachea
Only when epiglottis closes-
Upper oesophageal sphincter relaxes

62
Q

What is the purpose of each part of the pharyngeal phase?

A

Protect the respiratory system
soft palate elevates- to protect the nasal passages
epiglottis closes trachea- protects trachea passages

63
Q

Process of swallowing: Oesophageal phase

A

Upper oesophageal sphincter closed
peristalsis starts
getting food from oesophagus to stomach

64
Q

What is peristalsis

A

sequential contraction of ring of muscle

Inner circular muscle of the muscularis externa contracting behind the bolus of food and relaxed smooth muscle in front

65
Q

How is the upper and lower oesophageal sphincters coordinated?

A

When upper opens lower closes

vice versa

66
Q

How is the stomach distinguished by mobility?

A

Orad

Orad and Caudad

67
Q

What is the Orad of the stomach used for?

A

Accommodation of food

68
Q

What is the Orad and Caudad of the stomach used for?

A

Gastric emptying

69
Q

Where is the Orad of the stomach located?

A

Top of the stomach

70
Q

Where is the Caudad of the stomach located?

A

Bottom of the stomach

71
Q

What happens to either Orad or caudad during swallowing and what is this known as?

A

Relaxing of the Orad

Receptive relaxation

72
Q

What is receptive relaxation and its function

A

Relaxing of the Orad of the stomach

to accomodate food coming down the oesophagus

73
Q

Process of vomiting

A 
Reverse peristalsis
Pyloric sphincter and stomach relaxes
forced inspiration
occurs against a closed epiglottis
This gives a Sharply elevated intra abdominal pressure with forceful contraction of abdominal  muscles 
vomit propels up the oesophagus 
reflex relaxation of upper oesophagus sphincter 
Induces vomiting
74
Q

What does a forced inspiration against closed epiglottis achieve in vomitting?

A

Lowering of the diaphragm
Decreases intrathoracic pressure
intra abdominal pressure goes up

75
Q

Motility in the stomach

A

Peristalsis
Contractions begin in the corpus and travel toward the pylorus (propulsion)

They increase in force and velocity as they approach the gastroduodenal junction

Grinding occurs mainly in the antrum

Retropulsion is very effective at mixing and breaking down gastric contents

76
Q

What is propulsion

A

wave s of contractile activity in the muscularis externa

77
Q

What is grinding in the stomach?

A

Mixing of foodstuff into smaller and smaller parts

78
Q

What is retropulsion

A

Where after contractile waves hit pylorus sphincter it returns and travels through lumen of the stomach

79
Q

Motility in the Small Intestine

A

Non-propulsive movements-The most frequent type of movement in the small intestine
Caused by rhythmic contraction and relaxation of the muscularis externa
Effectively mixes chyme and brings digested nutrients into contact with the mucosal surface
Aids digestion more than moving it

Peristalsis-
Occurs at low frequency
Caused by contraction of successive sections of muscularis externa
Propels chyme for a short distance, allowing time for digestion and absorption

80
Q

Motility of the large intestine

A

Mixing the chyme, to improve the absorption of water and salts from the colon
Kneading the semisolid contents

Segmentation
Mass movement or mass peristalsis

81
Q

What is segmentation

A

Moving contents towards anus slowly

82
Q

What is Moving contents towards anus slowly termed as?

A

segmentation

83
Q

What is the rate that contents are moved towards the anus?

A

5-10cm/hour

84
Q

How is motility of the large intestine controlled?

A

Directly controlled by enteric nervous system except for control of defecation

85
Q

Where is the absorption of salt and water predominately done?

A

Ascending and transverse column of the large intestine

86
Q

How many times does mass peristalsis happen per day in the large intestine? Why?

A

1-3/ day

to move waste material to the rectum

87
Q

What is the special movement that moves colonic content towards the anus?

A

Mass of peristalsis

88
Q

How much does contents are moved towards the anus with mass peristalsis?

A

20cm

89
Q

What is the gastrocolic reflex

A

distention of the wall of the stomach initiates a mass peristalsis

90
Q

What is duodenocolic reflex

A

distention of the wall of the duodenum initiates a mass peristalsis

91
Q

Defaecation

A

distention of the wall of the rectum
rectosphincteric reflex happening
Relaxation of the internal anal sphincter (Contraction of external anal sphincter if not wanting to defaecate)
Relaxation of external anal sphincter
Contraction of abdominal wall muscles and relaxation of pelvic wall muscles
flexure of hips and descent of pelvic floor

92
Q

What is defaecation also known as?

A

Retcosphincteric reflex

93
Q

How do you initiate the rectosphincteric reflex

A

By filling of the rectum with faeces
Distention of the rectum wall
Putting a balloon in the rectum and inflating that balloon

94
Q

Retcosphincteric reflex

A

Activated stretch receptors in the rectum
signalling by the afferent pelvic nerves back to the sacral spinal cord
signalling back to the rectum esp. external anal sphincter via pudendal somatic motor nerve fibres

Gastrointestinal Case (11 decks)

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