small inestine Flashcards

1
Q

what is it made up of

A

duodenum
jejunum
ileum

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2
Q

how is the surface area increased

A

mucosal folds called villi

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3
Q

how is the surface area on villi increased

A

microvilli

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4
Q

what does villus core contain

A
  • blood vessels
  • lacteals
  • cells
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5
Q

what are the spaces between the villi called

A

crypts of Lieberkuhn

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6
Q

where are enterocytes formed

A

at the bottom of the crypts

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7
Q

where do enterocytes migrate to

A

tops of the villi

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8
Q

what is the blood supply to the small intestine via

A

branches of the superior mesenteric artery

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9
Q

what are the terminal branches

A

end arteries

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10
Q

are there anastomoses in small intestine

A

no

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11
Q

what does the enteric nervous system coordinate

A
  • absorption
  • secretion
  • blood flow
  • motility
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12
Q

what are the 2 plexus of the enteric nervous system

A

myenteric

submucosal

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13
Q

how does the enteric nervous system communicate with the central nervous system

A

via the autonomic afferent and efferent pathways

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14
Q

where do interstitial cells of cajal lie within

A

smooth muscle

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15
Q

when does migrating motor complex occur

A

during fasting

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16
Q

how many phases is the MMC

A

3

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17
Q

how long does MMC cycle last

A

90 minutes

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18
Q

what is MMC like after a meal

A

irregular lasts for 2-5 hours

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19
Q

what cells secrete CCK

A

I cells

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20
Q

what does CCK cause

A

gall bladder contraction and sphincter of oddi relaxation

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21
Q

what cells secrete gastrin

A

G cells

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22
Q

what does gastrin stimulate

A

acid secretion

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23
Q

what cells secrete secretin

A

S cells

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24
Q

what does secretion stimulate

A

pancreatic bicarbonate secretion

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25
Q

what releases glucagon

A

alpha cells

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26
Q

what does glucagon do

A

opposes insulin in blood glucose control

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27
Q

what cells secrete VIP

A

enteric nerves

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28
Q

what cells secrete GIP

A

K cells

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29
Q

what does GIP cause

A

greater insulin release by islets

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30
Q

what cells release glucagon-like peptide-1

A

L cells

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31
Q

what does GLP1 cause

A

insulin synthesis

inhibits glucagon secretion and gastric emptying

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32
Q

what cells release pancreatic polypeptide

A

PP cells

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33
Q

what does pancreatic polypeptide cause

A

inhibits pancreatic and biliary secretions

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34
Q

what cells secrete peptide YY

A

L cells

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35
Q

what does peptide YY do

A

inhibit pancreatic exocrine secretion

reduces food intake and appetite

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36
Q

what does motilin do

A

increase gastric emptying and small bowel contraction

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37
Q

what does ghrelin do

A

stimulate appetite, increase gastric emptying

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38
Q

what does obestatin do

A

opposes ghrelin

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39
Q

what does oxyntomodulin do

A

inhibit appetite

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40
Q

what cells secrete somatostatin

A

D cells

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41
Q

what does somatostatin do

A

inhibit secretion and action of most hormones

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42
Q

what cells secrete insulin

A

pancreatic beta cells

43
Q

what does insulin do

A

increases glucose utilisation

44
Q

what do epithelial cells of small bowel form

A

physical barrier that is selectively permeable to ions

45
Q

what cells produce protease and disaccharides

A

intestinal cells

46
Q

what organ produces lipase

A

pancreas

47
Q

does simple diffusion require energy

A

no

48
Q

when does simple diffusion take place

A

when there is a concentration gradient

49
Q

where is vitamin B12 absorbed

A

jejunum

50
Q

what kind of concentration gradient does facilitated diffusion need

A

that down a concentration gradient

51
Q

example of facilitated diffusion

A

fructose transport

52
Q

what is sodium/glucose transporter called

A

SGLT1

53
Q

what is SGLT1 powered by

A

energy from the flow of Na+ ions

54
Q

how does glucose leave the cell

A

through GLUT 2

55
Q

where is GLUT2

A

basolateral membrane

56
Q

what do dietary carbohydrates consist mainly of

A

starch

57
Q

what is starch

A

polysaccharide

58
Q

what must starch be converted to for absorption

A

monosaccharide

59
Q

what is polysaccharide breakdown catalysed by

A

salivary amylase

60
Q

what are the breakdown products of starch

A

maltose and maltotriose
sucrose
lactose

61
Q

what is dietary protein digested by

A

pancreatic proteolytic enzymes

62
Q

what is dietary protein broken down into

A

amino acids and peptides

63
Q

what does dietary fat consists of

A

triglycerides mainly

some cholesterol and fat soluble vitamins

64
Q

how is fat emulsified

A

by mechanical action in the stomach

65
Q

what does bile do

A

solubilise fat and promote hydrolysis of triglycerides

66
Q

what is it called when there is a cluster of bile acids, phospholipids and products of fat digestion

A

mixed micelles

67
Q

what is trapped in the centre of a micelle

A

hydrophobic monoglycerides, fatty acids and cholesterol

68
Q

what do unabsorbed lipids do to gastric emptying

A

delay it via peptide YY to allow more time for absorption

69
Q

what are medium chain triglycerides transported via

A

portal vein

70
Q

what is the absorption of water and electrolytes coupled with

A

monosaccharides, amino acids and bicarbonate

71
Q

what does commensal bacteria maintain

A

the integrity of the small bowel

72
Q

what makes up the physical defence

A
  • mucus layer
  • continous shedding of surface epithelial cells
  • physical movements of luminal contents
  • colonisation resistance
73
Q

what cells secrete lysosomes and phospholipase A2

A

paneth cells at the base of crypts

74
Q

what cells secrete trefoil peptides

A

goblet cells

75
Q

what is the principal mucosal antibody

A

IgA

76
Q

how does IgA mediate mucosal immunity

A

agglutinating and neutralising pathogens in the lumen

77
Q

what is IgA secreted from

A

immunocytes in the lamina propria

as dimers

78
Q

how are antigens from the bowel transported by

A

M cells and dendritic cells

79
Q

what do activated B cells produce

A

IgA

80
Q

what does lamina propria contain mostly

A

CD4

81
Q

what are most common symptoms of small bowel disease

A
  • diarrhoea
  • steatorrhoea
  • abdominal pain
  • weight loss
  • nutritional defences
82
Q

when does steatorrhoea occur

A

when stool is fat

83
Q

what do stools look like in steatorrhoea

A

pale, bulky and offensive and float leaving a fatty film on the water

they are difficult to flush away

84
Q

what is weight loss due to

A

anorexia

occurs because of malabsorption

85
Q

what are nutritional defences of

A
  • iron
  • vitamin B12
  • folate
86
Q

what does nutritional deficiencies lead to

A

anaemia

87
Q

what does vitamin K deficiency cause

A

bruising

88
Q

what does calcium deficiency cause

A

tetany

89
Q

what does vitamin D deficiency cause

A

osteomalacia

90
Q

what symptoms can multiple deficiencies cause

A
  • stomatitis
  • sore tongue
  • aphthous ulceration
91
Q

what deficiency can occur in Crohn’s

A

vitamin B12

92
Q

what disease of small intestine cause malabsorption

A
  • coeliac disease
  • dermatitis herpetiformis
  • tropical sprue
  • Whipple’s disease
  • radiation enteropathy
  • parasite infestation
93
Q

examples of anaerobic bacteria

A

anaerobes

e.g. bacteroides

94
Q

what’s more abundant anaerobic or aerobic

A

anaerobic

95
Q

what is function of the gut microflora

A

fermentation of non-digestible dietary residues into short chain fatty acids

96
Q

what does bacteria initiate

A

vitamin K production

97
Q

is the upper part of the intestine sterile

TRUE or FALSE

A

true

98
Q

what bacteria does the terminal ileum contain mainly

A

e.coli

99
Q

what does a bacterial overgrowth occur with

A

stricture or diverticulum

100
Q

what are clinical features of overgrowth

A
  • diarrhoea

- steatorrhoea

101
Q

why does steatorrhoea occur with bacterial overgrowth

A

conjugated bile salt deficiency

102
Q

why can B12 deficiency occur with bacterial overgrowth

A

bacteria cna metabolise vitamin B12 and interfere with its binding to intrinsic factor

103
Q

how to treat bacterial overgrowth

A

antibiotics such as metronidazole, tetracycline or ciprofloxacin