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Flashcards in Motility of GI tract Deck (50):
1

what are sphincters?

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

2

What are the 4 layers of the gut wall

Mucosa
submucosa
Muscularis externa
Serosa

3

Describe the mucosa layers

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

4

Describe the submucosa

Large Blood vessels and lymphatics
Submucosal nerve plexus-regulates blood flow and secretion

5

describe the muscularis externa

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

6

Serosa

Connective tissue & connects to abdominal wall supporting GI tract

7

GI innervation: what does the ENS do

Controls gut motility
innervates longitudinal and circular muscle

8

describe extrinsic pathway

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

9

Describe the intrinsic pathway

The Myenteric plexus-between circular and longitudinal muscle layers

10

What does the myenteric plexus innervate

Longitudinal muscles and outer lamella of circular muscles

11

What's Hirschsprungs disease

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

12

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

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

13

Force of contraction in sync with

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

14

What are the 3 types of gut motility patterns

Segmentation
Tonic contraction
Peristalsis

15

What does segmentation do

Small intestine-mix chyme with enzymes and fragment bolus
No net forward movement

16

What does intestinal peristalsis do

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.

17

What triggers peristalsis

Distention of gut

18

what is MMC

Migrating motor complex

19

WHat rlly is mmc

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

20

What is the purpose of MMC

Prevents colonisation of upper intestine

21

Does MMC require External innervation

No its an intrinsic property

22

What is paralytic ileus ?

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

23

Movement along GI- what is another word for swallowing

Deglutition

24

Describe the process of swallowing

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

OesophagL MOTILITY: WHAT 3 STEPS OCCUR

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

What occurs in Gastro-Esophageal reflux disease

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

27

What occurs when theres dysfunction in esophageal motiity

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

28

what are the 3 functions and motility of stomach

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

What regulates gastric peristalsis

Pace maker cells
in mid portion of greater curvature

30

Describe receptive relaxation:

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

What is receptive relaxation mediated by

Vagus nerve

32

Describe Mixing

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

How is the stomach motility regulated

1) distention- activates mechanoreceptors -extrinsic
2) gastrin release in response to food in stomach and therefore motility

34

Describe stomach emptying

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

How do we control the emptying

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

Control of stomach emptying -whats the hormonal pathway

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

What is the neural pathway of emptying

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

What is dumping syndrome

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

39

What is Gastroparesis

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

40

Motility in small intestine: what are the 2 major functions

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

Peristalsis-propulsion -short range contractions

41

Small intestine Motility dysfunction describe 1

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

42

Motility in large intestine: describe

Slow and regular to increase contact with absorbing surface

43

What are the thick bands in large intestine muscles called

(3-muscles)- Taeha coli

44

What are haustrations

Segmental contractions of circular muscles that divide colon into segments

45

What occurs in the descending colon

Propulsive movement via peristalsis

46

What is mass movement

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

Rectum and defecation: what is main process

Mass movement

48

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

1-internal and external anal sphincter contract
internal involuntary but external voluntary

49

Is rectum controlled by afferent stim

Yes- via parasympathetic signal to relax sphincter

50

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

Reverse peristalsis occurs, driving faces back into colon