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GI (Y1) > GI tract & Motility - Week 1 > Flashcards

GI tract & Motility - Week 1 Flashcards

1
Q

What is the purpose of the mouth & oropharynx?

A

chops and lubricates food, starts carbohydrate digestion, propels food to oesophagus

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2
Q

What is the purpose of the oesophagus?

A

muscular tube - propels food to the stomach

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3
Q

What is the purpose of the stomach?

A

stores/churns food, continues carbohydrate and initiates protein digestion, regulates delivery of chyme to duodenum

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4
Q

What are the 3 components of the small intestine?

A

duodenum, jejunum and ileum

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5
Q

What is the purpose of the small intestine?

A

principal site of digestion and absorption of nutrients

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6
Q

What are the components of the large intestine?

A

caecum, appendix and colon

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7
Q

What is the purpose of the large intestine?

A

storage andColon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum

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8
Q

What is the purpose of the rectum and anus?

A

storage and regulated expulsion of faeces

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9
Q

What are the structures contained within the hepatobiliary system?

A

(i) salivary glands, (ii) the pancreas, (iii) the liver and gall bladder

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10
Q

Secretions from which organ enter the stomach?

A

Pancreas

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11
Q

Where are most absorptive cells found?

A

Duodeum and ileum

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12
Q

What are the 3 parts of the colon?

A

Ascending, transverse and descending

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13
Q

What is reabsorbed in the large intestine?

A

Water and electrolytes

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14
Q

What is meant by motility?

A

Mechanical activity mostly involving smooth muscle

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15
Q

The alimentary canal is made from smooth muscle apart from…

A

Mouth, pharynx, upper 1/3rd of oesophagus and external anal sphincter

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16
Q

Secretion is required for…

A

(i) digestion, (ii) protection and (iii) lubrication

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17
Q

What is meant by digestion?

A

Chemical breakdown by enzymatic hydrolysis of complex foodstuffs to smaller, absorbable, units

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18
Q

Give examples of secretions.

A

Liquid & electrolytes

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19
Q

What is meant by absorption?

A

Transfer of the absorbable products of digestion (with water, electrolytes and vitamins) from the digestive tract to the blood, or lymph

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20
Q

What are the 4 general layers of the alimentary canal?

A

Mucosa, sub-mucosa, muscularis externa, serosa

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21
Q

Which cells are contained within mucosa?

A 
epithelial cells
exocrine cells
endocrine gland cells
lamina propria (capillaries, enteric neurones, immune cells)
muscularis mucosae
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22
Q

Intestinal absorption cells are called…

A

Enterocytes

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23
Q

What are the components of submucosa?

A 
connective tissue
larger blood and lymph vessels
glands
nerve network
submucous plexus
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24
Q

Where is the submucous plexus found?

A

Submucosa

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25
Q

What is contained within muscularis externa?

A

circular muscle layer
nerve network
myenteric plexus
longitudinal muscle layer

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26
Q

Where is the myenteric plexus found?

A

Muscularis externa - between circular muscular layer and longitudinal muscular layer

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27
Q

What is the role of the muscularis mucosae?

A

can change the shape of the mucosa for mixing contents of the lumen

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28
Q

What is the purpose of the serosa?

A

squamous cells produce lubricant which helps abdominal organs to move over one another

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29
Q

Which adaptation in structure is made by the stomach?

A

additional oblique smooth muscle layer in stomach

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30
Q

What is the overall length of the GI system?

A

7-10m

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31
Q

What is the effect of Circular muscle contraction?

A

lumen becomes narrower and longer

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32
Q

What is the effect of Longitudinal muscle contraction?

A

intestine becomes shorter and fatter

33
Q

What is the effect of Muscularis mucosae contraction?

A

change in absorptive and secretory area of mucosa (folding), mixing activity

34
Q

How are SM cells in the GI tract held together?

A

Gap junctions

35
Q

Gap junctions electrically couple adjacent cells allow…

A

slow wave of depolarization to spread across muscle sheet

36
Q

Spread of electrical currents from cell to cell forms…

A

Functional syncytium

37
Q

Spontaneous activity across the syncytium is driven by…

A

interstitial cells of Cajal (ICCs) - pacemaker cells interspersed between smooth muscle cells (SMCs)

38
Q

Spontaneous activity across the syncytium is altered by…

A

intrinsic (enteric) and extrinsic (autonomic) nerves

numerous hormones

39
Q

Contraction only occurs if the slow wave amplitude is…

A

sufficient to trigger SMC action potentials

40
Q

Upstroke of the slow wave is mediated by…

A

voltage-activated Ca2+ channels

41
Q

Downstroke of the slow wave is mediated by…

A

voltage-activated K+ channels

42
Q

ICCs are located…

A

between the longitudinal and circular muscle layers and in the submucosa

43
Q

ICCs form gap junctions with…

A

each other and smooth muscle cells

44
Q

Basic electrical rhythm (BER) is determined by…

A

Slow waves

45
Q

Whether slow wave amplitude reaches threshold depends upon…

A

Neuronal stimuli
Hormonal stimuli
Mechanical stimuli

46
Q

What is the BER frequency of the stomach?

A

3/min

47
Q

What is the BER of the small intestine?

A

8-12/min

48
Q

BER in the small intestine tends to drive contents in which direction?

A

Aboral direction

49
Q

What is the BER frequency of the large intestine?

A

8-16/min

50
Q

In which direction does BER drive contents in the large intestine?

A

Proximal and distal

51
Q

Why is BER proximal and distal in the large intestine?

A

favours retention of luminal contents facilitating reabsorption of water and electrolytes

52
Q

What is the meaning of aboral?

A

Away from the mouth

53
Q

What is meant by BER?

A

Basic Electrical Rhythm

54
Q

Post ganglionic parasympathetic fibres from which spinal nerves innervate the enteric nervous system?

A

S2-4

55
Q

What is the effect of parasympathetic autonomic innervation on the GI tract?

A

Increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction. Relaxation of some sphincters, receptive relaxation of stomach.

56
Q

What is the effect of sympathetic autonomic innervation on the GI tract?

A

Increased sphincter tone & Decreased motility, secretion and blood flow

57
Q

Sympathetic autonomic innervation of the GI tract arises from the…

A

Thoracolumbar region

58
Q

What are the 3 sympathetic nerves which innervate the GI tract?

A

Coeliac, superior mesenteric and inferior mesenteric

59
Q

Ganglia in the Myenteric (Auerbach’s) plexus primarily regulates…

A

motility and sphincters

60
Q

Ganglia in the Submucous (Meissner’s) plexus mainly regulates…

A

epithelia and blood vessels

61
Q

Sensory neurones from the GI tract relay back to…

A

Sympathetic ganglia

62
Q

What is the purpose of interneurones?

A

co-ordinating reflexes and motor programs

63
Q

What is the purpose of motor neurones in the GI tract?

A

excitatory and inhibitory motor neurones supplying both smooth muscle layers, secretory epithelium, endocrine cells and blood vessels

64
Q

The ENS refers specifically to….

A

cell bodies within myenteric or submucosal plexus

65
Q

What is meant by a local reflex?

A

Intrinsic

66
Q

What is meant by a short reflex?

A

Extrinsic passing through pre-vertebral ganglia

67
Q

What is meant by a long reflex?

A

Extrinsic passing through medulla oblongata

68
Q

Give an example of a local reflex.

A

Peristalsis

69
Q

Give an example of a short reflex.

A

intestino-intestinal inhibitory reflex

70
Q

Give an example of a long reflex.

A

gastroileal reflex

71
Q

What is meant by peristalsis?

A

a wave of relaxation, followed by contraction, that normally proceeds along the gut in an aboral direction – triggered by distension of the gut wall

72
Q

Explain what happens behind food in peristalsis.

A

Motor neurone activation causes Longitudinal muscle to relax and circular muscle to contract

73
Q

Explain what happens in front of food in peristalsis.

A

Altered activity of motoneurones –> Longitudinal muscle contracts & Circular muscle relaxes

74
Q

What is meant by segmentation?

A

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

75
Q

Where does segmentation usually occur?

A

Small intestine

76
Q

When segmentation takes place in the large intestine, this is called…

A

Haustration

77
Q

What is meant by Migrating motor complex (MMC)?

A

powerful sweeping contraction from stomach to terminal ileum

78
Q

What is meant by tonic contractions?

A

Sustained contractions - high pressure in sphincters and low pressure in storage organs

79
Q

Name the 6 sphincters of the GI tract.

A

Upper oesophageal sphincter, lower oesophageal sphincter, pyloric sphincter, ileocaecal valve, internal and external anal sphincters

GI (Y1) (79 decks)

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