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medicine > GI > Flashcards

GI Flashcards

1
Q

Mucosal sites, containing specialised lymphoid tissues

A

Appendix, large intestine, peyer’s patch in small intestine, adenoid and tonsils

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2
Q

Function of GI tract

A
  1. food digestion and absoprtion

2. immune regulation

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3
Q

GI tract: regards to immune functions

A
  1. portals of entry for non pathogenic antigens thus requires highly selective defense mechanisms
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4
Q

Polarised columner momolayer separating microbiota from lamina propria consists of? 5 things

A
  1. enteroabsorptive cells
  2. Goblet cells
  3. neuroendocrine cells
  4. Paneth cells
  5. M cells
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5
Q

Small intestine includes…

A 
villi and crypts 
goblet cells-mucus
Paneth cells-defensins
peyer's patches
Nutrient absoprtion
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6
Q

What do peyer’s patches do?

A 
antigen sampling (capture) and immune activation
contain immune cells
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7
Q

Large intestine includes…

A 
higher bacterial load
only crypts, no villi
No paneth cells
Enterocytes do defense
lots of goblet cells
No peyer's patches
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8
Q

Where are paneth cells found?

A

in base of crypts

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9
Q

Intestinal epithelial associated

A

innate immunity, antigen capture and effector function

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10
Q

Antigen capturing: where can it occur?

A

peyer’s patches and directly across the epithelial layer (by dendritic cells)

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11
Q

Peyers patches are covered by what?

A

An epithelial layer containing M cells (which have characteristic membrane ruffles)

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12
Q

three steps to M cell taking up antigen

A

M cell takes up antigen by endocytosis and phagocytosis
antigen transported across the M cell in vesicles and released at the basal surface
Antigen bound to dendritic cell –> activates T cell

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13
Q

where do microorganisms and particles get drained to in the gut

A

mesenteric lymoh nodes

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14
Q

lymphoid tissue in gut contains large numbers of?

A

B cell follicles

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15
Q

How do T cells enter peyers patches from blood vessel

A

homing receptors: CCR7 and L-selectin

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16
Q

Once activates in gut associated lymphoid tissue the niave T cell loses….

A

CCR7 (thus can not longer recirculate)

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17
Q

Most common antibody in the lamina propria of gut…

A

IgA

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18
Q

How does T cell get from blood vessel to Small or large intestine?

A
  1. T cell binds to MAdCAM-1 on endothelium

2. Gut epithelium express chemokines specific for gut-homing T cells

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19
Q

if small intestine is point of entry T cell contains…

A

CCR9

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20
Q

if large intestine is point of entry T cell contains…

A

CCR10

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21
Q

Order of Ig in intestine: from most to least

A

IgA, IgM and IgG

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22
Q

Intraepithelial lymphocytes are?

A

90% T cells –> 80% CD8

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23
Q

Two different recognition mechanisms in intraepithelial if intestine

A
  1. Virus specific - TCR/CD8

2. Stress specific recognition- NK cells

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24
Q

Special T cells in gut?

A

intra-epithelial lymphocytes (lie within lining of gut)

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25
Q

Proposed mechanisms of mucosal hyporesponsiveness

A

Deletion of antigen specific T cells
Generation of T cells ie. CD4
b cell –> IgA
commensal organisms

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26
Q

Maintaining the balance between protective immunity and homeostasis

A
  1. means of discriminating between pathogen and innocuous antigens
  2. oral tolerance
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27
Q

how does commensal organisms lead to hyporesponsiveness?

A

Dendritic cell doesnt mature , gives weak co-stimulation signals ans induce CD4 cell to diff into regulatory Th3 or Treg cells, instead of effector Th1 or Th2 cells

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28
Q

Mucosal response to infection. 3 points

A
  1. NFkB pathway activated by PRR (intracellular sensors in epithelial cells)
  2. Gene transcription and production of cytokines, chemokines and defensins
  3. Activate underlying immune response
29
Q

What kind of disorder is coeliac?

A

Autoimmune disorder

30
Q

What does coeliac disease do?

A

Damages small intestine –> malnutrition
not allergy
incurable

31
Q

What does the presents of gluten cause the mucosal epithelial cells to express?

A

MIC molecules (activates the intraepithelial lymphocytes to kill the epithelial cells)

32
Q

Digestion of peptides, bound to gluten. 3 steps.

A
  1. enzyme, tissue transglutaminase (tTG) modifies peptides so they can bind to MHC II
  2. bound peptide activates gluten-specific CD4 T cells
  3. kill mucosal epithelial cells by binding Fas.
    And. Secrete IFN-y- activates epithelial cells
33
Q

How to diagnosis coeliac disease

A

Biopsy (gold standard)
Serology - IgA anti-tissue transglutaminase autoantibodies
- dependant on dietary state of patient

34
Q

IBD: is imbalance of what?

A

improper development of the intestinal immune system and unable to prevent the invasion of harmful pathogens

35
Q

Ulcerative colitis features: where, type of inflammation, cytokine profile, smoking?

A

Colon, mucosal, Th2, IL-5/13, smoking is protective

36
Q

Crohns disease features: where, type of inflammation, cytokine profile, smoking?

A

Any part of GI tract (discontinuous), Transmural/granulomatous, Th1, IL23 and y-IFN, smoking increases risk

37
Q

Most common gene found if CD

A

NOD2

38
Q

What can you also get from UC?

A

arthritis/uveitis, skin lesions

39
Q

Where is UC most common?

A

Urbanised western societies

40
Q

Both UC and CD produce large amount of inflammatory….

A

cytokinesm IL-1, IL-6 and TNF alpha

41
Q

Biochemistry of liver metabolism

A

.

42
Q

Job of liver (6)

A
  1. first destination of most nutrients and xenobiotics absorbed from the gut
  2. Bile production
  3. Elimination of unwanted molecules -into biliary tree and faecal excretion
  4. Secretion of plasma proteins (albumin)
  5. Storage of important molecules (iron, vits etc)
  6. regulation of metabolism
43
Q

What allows the separation of proteins by size?

A

electrophoresis

44
Q

Examples of plasma proteins separated in electrophoresis

A

albumin, alpha, beta and gamma globulins

45
Q

Main functions of plasma proteins (5)

A
  1. Maintenance of oncotic and colloid osmotic pressure
  2. Transport of hydrophobic substances- steroid hormones, free fatty acids, bilirubin, cholesterol
  3. pH buffering- AA side chains can carry net charges
  4. Enzymatic - blood clotting
  5. immunity
46
Q

What does the maintenance of oncotic and colliod osmotic pressure ensure?

A

ensures they do no exit into interstitial fluid and prevents loss of plasma proteins

47
Q

What does alpha globulins do?

A

transport lipoproteins, lipids, hormones and bilirubin.

it is a retinol binding protein- transports vit A

48
Q

Example of alpha globulin

A

ceruloplasmin

49
Q

What is retinal binding protein?

A

lipid soluble alcohol, converted to retinaldehyde, part of rhodopsin, a visual pigment
Deficiency = visual impair

50
Q

Two types of B-globulins

A

transferrin and fibrinogen

51
Q

what does tranferrin do?

A

Transports Fe3+

indicator of iron deficiency

52
Q

What does fibrinogen do?

A

inactive for on fibrin, which is involved in the clotting of the blood

53
Q

what is the most abundant plasma protein?

A

Albumin

54
Q

what is albumin?

A

small, negatively charged, water-soluble
50% of plasma protein
main determinant of plasma oncotic pressure

55
Q

where is albumin made?

A

liver (14g per day)

56
Q

what stimulates the production?

A

insulin

57
Q

in albumin levels high or low in liver disease

A

low (starvation or low protein diet also causes decrease of levels)

58
Q

Transport functions of albumin

A

multiple binding sites for hydrophobic molecules .
Hydrophobic clefts in globular domains.
Low affinity, but high copacity due to high conc.

59
Q

What does albumin transport?

A

Fatty acids, bilirubin, thyroid hormones, exogenous substances (drugs, e.g. aspirin)

60
Q

where is iron stored?

A

in cells bound to ferritin

61
Q

why is iron important?

A

component of haem, myoglobin and cytochromes

62
Q

what is copper bound to for transport in blood?

A

ceruloplasmin

63
Q

why is copper needed?

A

regulation of redox reactions, transport and use of iron

64
Q

Deficiency in copper?

A

wilson’s disease

65
Q

Where are steroid hormones derived from?

A

cholesterol

66
Q

steroid hormones and T3/T4 thyroid hormones are hydrophilic or hydrophobic

A

hydrophobic

67
Q

lipoproteins have a hydrophilic shell and hydrophobic core. what is in core and shell?

A

Core: cholesterol esters and triglycerides
Shell: polar lipids and apoproteins

68
Q

Lipoproteins is involved in fat transport between organs and tissues

A

yes

medicine (8 decks)

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