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Physiology > GI Intro To The Struct Of GI tract and motility > Flashcards

GI Intro To The Struct Of GI tract and motility Flashcards

1
Q

What are the compartments of the ailment are canal separated by

A

Sphincters

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2
Q

What su the motility and what are some types

A

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

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3
Q

What are secretion required for

A

Digestion

Protection

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4
Q

What do some sec contain

A

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

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5
Q

What is digestion

A

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

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6
Q

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

A

Polysacc –> monosacs such as glucose or galactose

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7
Q

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

A

Mediated by proteases, dipeptides

Broken to amino acids, dipeptides see

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8
Q

What mediates fat digestion and what is it broken down to

A

Mediated by lipases

Conv to monoglycerides and free fatty acids

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9
Q

What are the layers on the digestive tract wall

A

Mucosa
Su mucosa
Muscular is external
Serosa

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10
Q

What is the mucosal layer

A

Epi cells
Exocrine cells
Endocrine gland cells
Lamina propria

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11
Q

What is in the sub mucosa layer

A

Connective tissue
Larger blood and lymp vessels
Glands
Myenteric nerve network

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12
Q

What is the muscularis external layer

A

Circular muscle layer
Myentericplexus
Longitudinal muscle layer

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13
Q

What is the Serosa layer

A

Connective tissue

Forms thin and sticky fluid lubricates outer surface

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14
Q

What is the gastrointestinal motility largely due to

A

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

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

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15
Q

What action does the circular and longitudinal muscle do

A

Circular - lament narrow and longer

Longitudinal- shorter and fatter

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16
Q

How are adjacent smooth muscle cells coupled

A

Via gap junctions whic allow spread of electrical activity

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17
Q

How is the rhythm of the GI muscle cells

A

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

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18
Q

How does spontaneous electrical activity portray in the intestines

A

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

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19
Q

What does the slow wave activity determine

A

Maximum frequency, direction and velocity of rythmic contractions

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20
Q

What are the slow waves driven by

A

Pacemaker cells interstitial cells of Cajal

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21
Q

Contraction only occurs if the slow waves…..

A

Amplitude sufficient trigger action potential in smooth muscle

22
Q

Force is related to whatn

A

Number of action potentails discharged

23
Q

Where are ICC’s found

A

Between longitudinal and circular muscle layers and in the submucosa

24
Q

What do the slow waves determine

A

The basal electrical rhythm

25
Q

Not all slow waves trigger

A

Contraction

26
Q

Whether slow wave amplitude aches threshold depends upon

A

Neural stimuli
Hormonal stimuli
Mechanical stimuli

27
Q

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

A

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

28
Q

Where are the neurones of the gut found

A

In ganglia in the Myenteric and submucous plexuses

29
Q

What connects the ganglia of the gut

A

Interganglionic fibre tracts

30
Q

What is the alternative name for Myenteric and submucous plexuses

A

Myenteric - auerbachs

Submucous - meissners

31
Q

What dos the enteric nervous system do

A

Coordinates muscular, secretive and absorptive activities

32
Q

How does the enteric nervous system do what it does

A 
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)
33
Q

What so the parasympathetic innervation of the GI tract

A

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

34
Q

What is the sympathetic innervation like in the GI tract

A 
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

35
Q

What is an example of a local reflex

A

Peristalsis

36
Q

What is an example of a short reflex

A

Intestino-intestinal inhibitory reflex

Local distension and command adjacent smooth muscle to relax

37
Q

What is an example of a long reflex

A

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

38
Q

What so peristalsis

A

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

39
Q

What is segmentation

A

Mixing or churning movements

Rhythmic contractions of the circular muscle layer that mix and divide luminal contents

40
Q

Where does segmentation occur

A

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

41
Q

What are tonic contractions

A

Sustained contractions found in the sphincters of the GI tract

42
Q

How many sphincters of the GI tract

A

6

43
Q

What does a sphincter consist of

A

Specialised circular general smooth muscle

Are exceptions

44
Q

What do sphincters act as

A

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

45
Q

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

A

Skeletal and relaxes to allow swallowing and closes during inspiration

46
Q

What does the lower esophageal sphincter do

A

Relaxes to permit food into stomach

Closes to prevent reflux of gastric contents to esophagous

47
Q

What dos the pyloric sphincter do

A

Regulates gastric emptying

Usually prevents duodenal gastric reflux

48
Q

What does the illeocecal sphincter do

A

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

49
Q

What so the difference between the internal and external anal sphincters

A

Internal - smooth muscle

External - skeletal muscle

50
Q

How are the two anal sphincters regulated

A

By the defecation reflex

51
Q

What is the direction of the food bolus

A

Oral to aboral

Physiology (28 decks)

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