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104:theme 1 > Motility of GI tract > Flashcards

Motility of GI tract Flashcards

1
Q

what are sphincters?

A

Smooth muscle, that hold luminal content adequately before emptying into next segment

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2
Q

What are the 4 layers of the gut wall

A

Mucosa
submucosa
Muscularis externa
Serosa

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3
Q

Describe the mucosa layers

A

Epithelial layer-endocrine-mucus
Lamina propria-VAN
GALT-Gut associated lymphoid tissue-
1-secretes antibiotics
2-Mucosa inflamm and damage
3-Provides permission of immunological tolerance
Muscularis mucosa- thin muscle that controls blood flow and GI secretion

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4
Q

Describe the submucosa

A

Large Blood vessels and lymphatics

Submucosal nerve plexus-regulates blood flow and secretion

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5
Q

describe the muscularis externa

A

Thick muscle-whose contractions contribute to major gut motility
2 substantial layers of smooth muscle cells

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6
Q

Serosa

A

Connective tissue & connects to abdominal wall supporting GI tract

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7
Q

GI innervation: what does the ENS do

A

Controls gut motility

innervates longitudinal and circular muscle

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8
Q

describe extrinsic pathway

A

t8-l2
preganglionic fibres
sympathetic activity inhibits gut motility and secretion and constics sphincters

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9
Q

Describe the intrinsic pathway

A

The Myenteric plexus-between circular and longitudinal muscle layers

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10
Q

What does the myenteric plexus innervate

A

Longitudinal muscles and outer lamella of circular muscles

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11
Q

What’s Hirschsprungs disease

A

Congenital absence of myeteric plexus-mainly in distal colon.
Resulting in spasms of large bowel-severe constipation

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12
Q

What is the BER-basic electrical rhythm/slow wave rhythm and where

A

Small intestine and distal stomach
Consists of spike potentials: Triggered if peak of slow wave depolarises membrane to threshold potential- opening of Ca2+ channels
it determines when contractions can occur

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13
Q

Force of contraction in sync with

A

Number of spikes within each wave = neural & hormonal input = 2 major types contractile responses : 1-segmentation and peristalsis

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14
Q

What are the 3 types of gut motility patterns

A

Segmentation
Tonic contraction
Peristalsis

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15
Q

What does segmentation do

A

Small intestine-mix chyme with enzymes and fragment bolus

No net forward movement

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16
Q

What does intestinal peristalsis do

A

Contraction of circular muscles behind bolus,
then contraction of longitudinal muscles in the middle of circular musces, ahead of bolus. Then contraction of circular muscles again hafway through when longitudinal muscles where contracting to force bolus forwards.

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17
Q

What triggers peristalsis

A

Distention of gut

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18
Q

what is MMC

A

Migrating motor complex

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19
Q

WHat rlly is mmc

A

Intervals of strong propulsive contractions, which pass down distal stomach & small intestine of indigestible materials.

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20
Q

What is the purpose of MMC

A

Prevents colonisation of upper intestine

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21
Q

Does MMC require External innervation

A

No its an intrinsic property

22
Q

What is paralytic ileus ?

A 
Temporary cessation of gut motility-
caused by-abdominal surgery
infection
drugs 
Signs and symp include: Nausea, vomiting and absent bowel sounds
23
Q

Movement along GI- what is another word for swallowing

A

Deglutition

24
Q

Describe the process of swallowing

A

Bolus formed via mastication
propelled to pharynx as tongue moves up & down, against hard palate
Only the above is voluntary rest is autonomic
Bolus stimulates mechanoreceptors in pharynx
Efferent impulses from vagus -pharynx
Soft palate ecevates and sup constrictor of pharynx contracts to close off nasopharynx
Resp inhibited
Larynx rises so epiglottis covers trachea
Upper Esophagal sphincter relaxes and bolus enters
Peristalic wave initiated in pharynx
If insufficient, vago-vagal reflex triggers 2nd

25
Q

OesophagL MOTILITY: WHAT 3 STEPS OCCUR

A

Upper oesophageal sphincter briefly relaxes allowing food bolus to pass into oesophagus

Contractile wave sweeps down

Lower esophageal sphincter & proximal stomach relax to allow bolus to enter stomach

26
Q

What occurs in Gastro-Esophageal reflux disease

A

Heart burn

When Lower esophageal sphincter-LES is incompetent, allowing flow of corrosive gastric juices into oesophagus

27
Q

What occurs when theres dysfunction in esophageal motiity

A

Achalasia- dysphagia, from failure of LES to relax: obstruction and Loss of peristalsis

28
Q

what are the 3 functions and motility of stomach

A

Storage - Ingest food faster than can be digestsed aided by receptive relaxation

Physical and chemical disruption-mixing

Deliver resultant chyme to intestine @ optimal rate- gastric emptying

29
Q

What regulates gastric peristalsis

A

Pace maker cells

in mid portion of greater curvature

30
Q

Describe receptive relaxation:

A

increase in stomach pressure triggering dumping & reflux
1st is relaxation-increase in fibre length ;muscle tone same, therefore increase in size and without increase in intragastric pressure,

31
Q

What is receptive relaxation mediated by

A

Vagus nerve

32
Q

Describe Mixing

A

Peristalsis via strong coord control of 3 muscle layers
As spread distally, force and speed increase
therefore little chyme goes into the duodenum but sphincter only transiently open, so back pressure in distal region- retropulsion

33
Q

How is the stomach motility regulated

A

1) distention- activates mechanoreceptors -extrinsic

2) gastrin release in response to food in stomach and therefore motility

34
Q

Describe stomach emptying

A

Terminal part- Pyloric ontrum has thickened muscle layers
Pyloric sphincter controls exit
Increase in chyme: antral contractions & opening of sphincters
Liquid then solid, each time small amounts into duedenum

35
Q

How do we control the emptying

A

1)small intestine has limited capacity- & only allows small amounts
2-via diff hormones to inhibit gastric emptying
3- Enterogastric reflex inhibits emptying & consists of complex hormonal and neuronal signals-stimulates pyloric contractions & increases tone of pyloric sphincter to prevent emptying

36
Q

Control of stomach emptying -whats the hormonal pathway

A

Presence of fatty acids/ monoglycerides, in duodenum & low PH stimulates release of hormones:

1) secretin - cause pancreas to secrete bicarb- decrease acid
2) GTP CCK-increase satiety by releasing bile, inhibiting gastric emptying
3) Enterogastrone-stop production of gastrin and acid produced

37
Q

What is the neural pathway of emptying

A 
Via ENS- presence of acid /fat, digestion products and hypertonic solutions are detected by:
Duodenal 
Mechano
Chemo
& osmo receptors 
This deceases sympathetic activity 
Increasing sympathetic activity 
or via ENS short reflex 
& fear anger depression...leads to change in gastric motor activity
38
Q

What is dumping syndrome

A

a gastric motility dysfunction-rapid emptying of gastric contents into small intestine causing nausea Pallor
Fainting after meal of hypotonic solution

39
Q

What is Gastroparesis

A

Impaired function of stomach to empty,
loss of vagal stimulation to stomach
abnormal bloating and nausea
In diabetics who develop neuropathy

40
Q

Motility in small intestine: what are the 2 major functions

A

Segmentation: Mixing- Mutiple shrt contractions from proximal to distal ileum. Decreases BER frequency to promote distal movement

Peristalsis-propulsion -short range contractions

41
Q

Small intestine Motility dysfunction describe 1

A

Intestinal blind loop syndrome:impaired small intestine peristalsis can lead to abnormally high levels of bacteria-diarrhoea

42
Q

Motility in large intestine: describe

A

Slow and regular to increase contact with absorbing surface

43
Q

What are the thick bands in large intestine muscles called

A

(3-muscles)- Taeha coli

44
Q

What are haustrations

A

Segmental contractions of circular muscles that divide colon into segments

45
Q

What occurs in the descending colon

A

Propulsive movement via peristalsis

46
Q

What is mass movement

A

Segmental contraction of right colon disappears & a simultaneous contraction of whole right colon propels food forward -occurs after a meal & is gastric colic reflex

47
Q

Rectum and defecation: what is main process

A

Mass movement

48
Q

When the stretch receptors of the rectum are distended what 2 things occur

A

1-internal and external anal sphincter contract

internal involuntary but external voluntary

49
Q

Is rectum controlled by afferent stim

A

Yes- via parasympathetic signal to relax sphincter

50
Q

What happens if voluntary relaxation of external sphincter doesn’t occur via pudendal nerve

A

Reverse peristalsis occurs, driving faces back into colon

104:theme 1 (6 decks)

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