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Gastrointestinal Case > Motility in the GI Tract > Flashcards

Motility in the GI Tract Flashcards

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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
What are sphincters
Specialised builging of the inner circular muscles from the muscularis externa
26
What do sphincters do?
separate two adjacent compartments of the GI tract Maintain positive resting pressure Regulate antegrade and retrograde movement Effectively serve as one-way valves
27
What does antegrade mean
Forward moving
28
What does retrograde mean
Backward moving
29
What are the sphincters ogf the GI tract
``` Upper oesophageal sphincter (UES) Lower oesophageal sphincter (LES) Pyloric sphincter Sphincter of Oddi Ileocecal sphincter Internal and external anal sphincters ```
30
Where is the Upper oesophageal sphincter (UES) located?
The top of the oesophagus
31
Where is the Lower oesophageal sphincter (LES) located?
At the bottom of the oesophagus
32
Where is the Pyloric sphincter located?
At the bottom of the stomach
33
Where is the Ileocecal sphincter located?
At the bottom of the small
34
Where is the Internal and external anal sphincters located?
At the rectum
35
How is the stomach isolated as a reservoir?
By the action of the Pyloric sphincter at the bottom and Lower oesophageal sphincter (LES) at the top
36
How is the action of the pyloric sphincter important
Regulating release of partially digested food from the stomach into the small intestine after a meal
37
How is the small intestine isolated as a reservoir?
By the action of the Pyloric sphincter at the top and Lower oesophageal sphincter (LES)
38
How is the small intestine isolated as a reservoir?
By the action of the Pyloric sphincter at the top and ileocecal sphincter at the bottom
39
How is the large intestine isolated as a reservoir?
By the action of the internal and external anal sphincter at the bottom and ileocecal sphincter at the top
40
Which sphincter is made of skeletal muscle and why is this important
External anal sphincter As for voluntary movement so don't automatically discharge. Go to the toilet
41
Where is the Sphincter of Oddi located
Wrapped around two ducts coming into the dduodenum: - - Pancreatic - biliary/ bile
42
What is the contraction of Sphincter of Oddi role
regulating delivery of pancreatic juice and bile from biliary system into duodenium
43
What is the epithelium of the oesophagus and why?
Stratified squamous epithelium | Protective mechanism from acid reflux from stomach
44
What are the type of sphincters are sphincters normally?
Anatomical
45
Which type of sphincter is the lower oesophageal sphincter
Physiological
46
What is the difference between an Anatomical and physiological sphincter?
Anatomically - bulging of the inner circular muscular layer | Physiological- no bulging but different in physiology
47
How is closure of the lower oesophageal sphincter achieved?
Contraction of the diaphragm intra-abdominal pressure is greater than the intra- gastric pressure anatomical organization of the gastrointestinal tract
48
What movement is more common in the GI tract antegrade or retrograde
Antergrade
49
How are the contraction of the sphincters cordinated?
smooth muscle contractions of adjacent compartments
50
What of the GI reflexes are voluntary
Swallowing reflex
51
Process of swallowing
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
What is a bolus of food
Food mixed with saliva
53
Where is the bolus of food is going to activate touch receptor
In the pharynx
54
When in the swallowing reflex does the reflex become involuntary
When medulla and pons is activated
55
Swallowing reflex- Once medulla and lower pons activated what controls the pharynx and upper oesophagus
cranial nerves
56
Swallowing reflex- Once medulla and lower pons activated what is controlled by the cranial nerves
pharynx and upper oesophagus
57
Swallowing reflex- Once medulla and lower pons activated what is controlled by the vagal nerves
Th rest of the oesophagus that is not the upper oesophagus
58
Swallowing reflex- Once medulla and lower pons activated what controls the rest of the oesophagus that is not the upper oesophagus
Vagal nerves
59
What are the three phases of swallowing
Oral phase/ Voluntary phase Pharyngeal phase Oesophageal phase
60
Process of swallowing: Oral phase/ Voluntary phase
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
Process of swallowing: Pharyngeal phase
soft palate elevates epiglottis closes trachea Only when epiglottis closes- Upper oesophageal sphincter relaxes
62
What is the purpose of each part of the pharyngeal phase?
Protect the respiratory system soft palate elevates- to protect the nasal passages epiglottis closes trachea- protects trachea passages
63
Process of swallowing: Oesophageal phase
Upper oesophageal sphincter closed peristalsis starts getting food from oesophagus to stomach
64
What is peristalsis
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
How is the upper and lower oesophageal sphincters coordinated?
When upper opens lower closes | vice versa
66
How is the stomach distinguished by mobility?
Orad | Orad and Caudad
67
What is the Orad of the stomach used for?
Accommodation of food
68
What is the Orad and Caudad of the stomach used for?
Gastric emptying
69
Where is the Orad of the stomach located?
Top of the stomach
70
Where is the Caudad of the stomach located?
Bottom of the stomach
71
What happens to either Orad or caudad during swallowing and what is this known as?
Relaxing of the Orad | Receptive relaxation
72
What is receptive relaxation and its function
Relaxing of the Orad of the stomach | to accomodate food coming down the oesophagus
73
Process of vomiting
``` 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
What does a forced inspiration against closed epiglottis achieve in vomitting?
Lowering of the diaphragm Decreases intrathoracic pressure intra abdominal pressure goes up
75
Motility in the stomach
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
What is propulsion
wave s of contractile activity in the muscularis externa
77
What is grinding in the stomach?
Mixing of foodstuff into smaller and smaller parts
78
What is retropulsion
Where after contractile waves hit pylorus sphincter it returns and travels through lumen of the stomach
79
Motility in the Small Intestine
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
Motility of the large intestine
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
What is segmentation
Moving contents towards anus slowly
82
What is Moving contents towards anus slowly termed as?
segmentation
83
What is the rate that contents are moved towards the anus?
5-10cm/hour
84
How is motility of the large intestine controlled?
Directly controlled by enteric nervous system except for control of defecation
85
Where is the absorption of salt and water predominately done?
Ascending and transverse column of the large intestine
86
How many times does mass peristalsis happen per day in the large intestine? Why?
1-3/ day | to move waste material to the rectum
87
What is the special movement that moves colonic content towards the anus?
Mass of peristalsis
88
How much does contents are moved towards the anus with mass peristalsis?
20cm
89
What is the gastrocolic reflex
distention of the wall of the stomach initiates a mass peristalsis
90
What is duodenocolic reflex
distention of the wall of the duodenum initiates a mass peristalsis
91
Defaecation
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
What is defaecation also known as?
Retcosphincteric reflex
93
How do you initiate the rectosphincteric reflex
By filling of the rectum with faeces Distention of the rectum wall Putting a balloon in the rectum and inflating that balloon
94
Retcosphincteric reflex
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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