GI Intro To The Struct Of GI tract and motility

Question 1

What are the compartments of the ailment are canal separated by

Answer 1

Sphincters

Question 2

What su the motility and what are some types

Answer 2

Mechanical activity mostly involving smooth muscle
( except skeletal muscle at mouth, pharynx, upper oes and external anal sphincter)

Propulsive movements oral to aboral
Mixing movements -
Tonic contractions

Question 3

What are secretion required for

Answer 3

Digestion

Protection

Question 4

What do some sec contain

Answer 4

Water ‘borrowed’ plasma
Electrolytes - sodium, pottasium, chloride
Organic compounds - bile salts, mucus, enzymes

Question 5

What is digestion

Answer 5

Chemical breakdown by enzyme hydrolysis of complex foodstuffs to smaller absorbable units

Question 6

What is carb digestion usually mediated by and what is it broken down to

Answer 6

Polysacc –> monosacs such as glucose or galactose

Question 7

What is the digestion of proteins mediated by and what are they broken down to

Answer 7

Mediated by proteases, dipeptides

Broken to amino acids, dipeptides see

Question 8

What mediates fat digestion and what is it broken down to

Answer 8

Mediated by lipases

Conv to monoglycerides and free fatty acids

Question 9

What are the layers on the digestive tract wall

Answer 9

Mucosa
Su mucosa
Muscular is external
Serosa

Question 10

What is the mucosal layer

Answer 10

Epi cells
Exocrine cells
Endocrine gland cells
Lamina propria

Question 11

What is in the sub mucosa layer

Answer 11

Connective tissue
Larger blood and lymp vessels
Glands
Myenteric nerve network

Question 12

What is the muscularis external layer

Answer 12

Circular muscle layer
Myentericplexus
Longitudinal muscle layer

Question 13

What is the Serosa layer

Answer 13

Connective tissue

Forms thin and sticky fluid lubricates outer surface

Question 14

What is the gastrointestinal motility largely due to

Answer 14

Activity of smooth muscle (circular, longitudinal layers and muscularis mucosal)

Skeletal muscle imp - mouth, pharynx, upper oes, external anal sphincter

Question 15

What action does the circular and longitudinal muscle do

Answer 15

Circular - lament narrow and longer

Longitudinal- shorter and fatter

Question 16

How are adjacent smooth muscle cells coupled

Answer 16

Via gap junctions whic allow spread of electrical activity

Question 17

How is the rhythm of the GI muscle cells

Answer 17

Intrinsic - enteric su mucosa plexus
Extrinsic autonomic nerves
Numerous hormones sec by endocrine cells of GI tract

Question 18

How does spontaneous electrical activity portray in the intestines

Answer 18

Slow waves - rhythmic patterns of mem depo and repo that spread from cell to cell via gap junctions

Question 19

What does the slow wave activity determine

Answer 19

Maximum frequency, direction and velocity of rythmic contractions

Question 20

What are the slow waves driven by

Answer 20

Pacemaker cells interstitial cells of Cajal

Question 21

Contraction only occurs if the slow waves…..

Answer 21

Amplitude sufficient trigger action potential in smooth muscle

Question 22

Force is related to whatn

Answer 22

Number of action potentails discharged

Question 23

Where are ICC’s found

Answer 23

Between longitudinal and circular muscle layers and in the submucosa

Question 24

What do the slow waves determine

Answer 24

The basal electrical rhythm

Question 25

Not all slow waves trigger

Answer 25

Contraction

Question 26

Whether slow wave amplitude aches threshold depends upon

Answer 26

Neural stimuli Hormonal stimuli Mechanical stimuli

Question 27

How many slow waves/min are in the Stomach Small intestine Large intestine

Answer 27

Stomach - 3 slow waves Small intestine - 10-12 waves in duo, 8 in ileum Large intestine - 8 in proximal colon, 16 distal colon

Question 28

Where are the neurones of the gut found

Answer 28

In ganglia in the Myenteric and submucous plexuses

Question 29

What connects the ganglia of the gut

Answer 29

Interganglionic fibre tracts

Question 30

What is the alternative name for Myenteric and submucous plexuses

Answer 30

Myenteric - auerbachs | Submucous - meissners

Question 31

What dos the enteric nervous system do

Answer 31

Coordinates muscular, secretive and absorptive activities

Question 32

How does the enteric nervous system do what it does

Answer 32

``` Via Sensory neurones specialised (mechanorecpe) Inter neurones (majority, coordinating reflexes) Effector neurones (excitatory and inhibitory Motor neurones supplying longitudinal and circular smooth muscle layers, sec epi, endocrine cells and blood vessels) ```

Question 33

What so the parasympathetic innervation of the GI tract

Answer 33

Preganglionic (ACh) synapse in ENS Excitatory - increased gastric, pans and small intestine sec, blood flow and smooth muscle contraction Inhibitory - relaxation of some sphincters, receptive relaxation of stomach

Question 34

What is the sympathetic innervation like in the GI tract

Answer 34

``` Preganglionic fibres (ACh) synapse at prevertebral ganglion Postganglionic releasing (NA) innervate mainly enteric structures also other structures ``` Functionally less lmp than parasymp Inhibitory - decreases motility, secretion and blood flow

Question 35

What is an example of a local reflex

Answer 35

Peristalsis

Question 36

What is an example of a short reflex

Answer 36

Intestino-intestinal inhibitory reflex | Local distension and command adjacent smooth muscle to relax

Question 37

What is an example of a long reflex

Answer 37

Increase gastric activity Increase propulsive activity in terminal ileum Food detected and causes contraction of terminal ileum propelled to large intestine

Question 38

What so peristalsis

Answer 38

A wave of contraction that normally proceeds along gut in a aboral direct triggered by distension of gut wall Contraction behind bolus and relaxation in front

Question 39

What is segmentation

Answer 39

Mixing or churning movements | Rhythmic contractions of the circular muscle layer that mix and divide luminal contents

Question 40

Where does segmentation occur

Answer 40

In small intestine and large intestine in fed state where called haustration

Question 41

What are tonic contractions

Answer 41

Sustained contractions found in the sphincters of the GI tract

Question 42

How many sphincters of the GI tract

Answer 42

6

Question 43

What does a sphincter consist of

Answer 43

Specialised circular general smooth muscle | Are exceptions

Question 44

What do sphincters act as

Answer 44

one way valves maintaining a positive resting pressure relative to two structures (eg oes and stomach)

Question 45

What is the upper esophageal sphincter made of and what does it do

Answer 45

Skeletal and relaxes to allow swallowing and closes during inspiration

Question 46

What does the lower esophageal sphincter do

Answer 46

Relaxes to permit food into stomach | Closes to prevent reflux of gastric contents to esophagous

Question 47

What dos the pyloric sphincter do

Answer 47

Regulates gastric emptying | Usually prevents duodenal gastric reflux

Question 48

What does the illeocecal sphincter do

Answer 48

Regulates the flow of ileum to colon Distension of ileum opens Distension of proximal colon closes

Question 49

What so the difference between the internal and external anal sphincters

Answer 49

Internal - smooth muscle | External - skeletal muscle

Question 50

How are the two anal sphincters regulated

Answer 50

By the defecation reflex

Question 51

What is the direction of the food bolus

Answer 51

Oral to aboral