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Pathobiology > Tissue Processing > Flashcards

Tissue Processing Flashcards

1
Q

Prognosis

A

Predicting the future course of the disease

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2
Q

Etilogy

A

What is the cause

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3
Q

Pathogenesis

A

Mechanisms/Evolution of disease

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4
Q

Morphology

A

Structural Changes in cell

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5
Q

What are the 3 main causes of cell injury

A

Acquired (Hypoxia/Ischaemia)

Genetic

Congenitial

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6
Q

Name the 3 types of lesion

A

Gross Lesion (naked eye)

Microscopic Lesion

Ultrastructural Lesion (EM)

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7
Q

Histology

A

Study of Normal Tissues/structure (liver)

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8
Q

Cytology

A

Study of Cells (blood smears)

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9
Q

Name the 3 methods of Pathology

A

Autopsy

Biopsy

Cytology

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10
Q

Name an example of a Biopsy Technique

A

Cervical Biopsy

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11
Q

Name a cytology Technique

A

Fine needle aspiration

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12
Q

Name the first 5 tissue processing steps

A

Fixation

Dehydration

Clearing

Wax infusion

Embedding

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13
Q

If using bone, what step goes between fixation and dehydration

A

Decalcification

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14
Q

Why is fixation done

A

Tissue deprived of blood supply

Therefore it will start to change

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15
Q

How is tissue affected thus needing fixation

A

Hypoxia

Putrefaction - Microorganisms growth = Microbial spoilage

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16
Q

Name 4 factors which affect fixation

A

Time

Temp

pH

Type of tissue

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17
Q

How can the pH be controlled in fixation technique

A

PBS buffer used in aldehyde buffers

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18
Q

Name 3 requirements of a good fixative

A

Go into cells quickly/evenly (tissue looks the same)

Not introduce artefacts to give false diagnosis

Harden tissue (make it responsive to subsequent treatment)

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19
Q

Why add calcium to fixative?

A

Preserve phospholipids

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20
Q

Name a type of fixative (F)

When is it used?

A

Formaldehyde (Formalin)

Light microscope

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21
Q

What is Formaldehyde mixed with?

Whats the final conc.

A

PBS to Neutral pH

4% Formalin

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22
Q

Name 2 Advantages of using Formalin

A

Retains natural colour

remains pliable for dissection

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23
Q

Name 2 disadvantages of using Formalin

A

Slow (12-24hrs)

Toxic - Formalin dematitis –>Carcinogenic agent

Not good for cytolplasmic stains

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24
Q

Name a type of Fixative (G)

When is it used?

A

Glutaraldehyde

EM

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25
Q

Name 2 advantages of Glutaraldehyde

A

Quicker than Formalin

Preerves intracellular organelles by inactivating all enzymes

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26
Q

Name 3 disadvantages of Glutaraldehyde

A

Penetration slower than Formalin

Difficult to remove–> Bad for immunohistochem

Inactivated all enzymes not good for EHC

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27
Q

Name a fixative useful for histochemisitry

A

Alcohols (Methanol/Ethanol)

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28
Q

What do Alcohol fixatives acheive? *(mechanism)

A

Denature proteins by removing water/replace with alcohol

Alteries tertiary shape but preserves chemical reactivitiy

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29
Q

When are Alcohol fixatives used

A

Histochemistry

Fixing smears

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30
Q

Name a oxidising agent fixative

A

Osmium tetraoxide

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31
Q

How do oxidising agents work as a fixative

A

Extensive denaturation of proteins

Stablizies lipids

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32
Q

When are oxidising agents used?

Whats a benefit

A

Lipid Preservation

Poor pentration/Dangerous for cornea

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33
Q

Mercuric Chloride

A

Zenker fluid

SH cross linking

Not good for ultra structures

Toxic

Produces black precipitate needs iodine

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34
Q

When are Mercuric Chlorides used?

A

Nuclear / cytoplasmic staining

35
Q

Why is Decalcification done?

Name a disease which the stage of decalcification can help towards

A

Examining minearlised tissues

Hydroxyapatite present

Osteosarcoma

36
Q

Name a decalficiation agent

A

Formic acid

EDTA

37
Q

Whats the benefit of using Chelating agents during decalcification?

Whats the downside

A

No damage to tissue

Takes a long time

38
Q

Why is dehydration done?

A

Water removed so paraffin can infiltrate tissue

39
Q

Whats the solution for dehydration consist of?

A

75% ethanol

25% PBS

40
Q

Why is Clearing done?

A

Removal of alcohol

As its MISCIBLE with the paraffin

41
Q

Name the most common clearing agent

A

Xylene

42
Q

When is Histo-clear used as a clearing agent?

A

Fine line tissue

43
Q

What does Wax infusion involve?

A

2-4 baths of Molten paraffin wax (55-60*) for several hours

44
Q

Why is embedding done?

A

Embeds tissue in support media for structural support

45
Q

Describe 2 features of paraffin

A

Long chain hydrocarbon

Similar hardness to tissue once impregnated into tissue

46
Q

Why is paraffin used?

A

Easier cutting

Structural support

Stored Indefinitely

47
Q

When Would plastic/resin be used as a wax?

A

Thinner sections can be cut

As it provides stronger support as its harder

48
Q

Name a type of embedding mould

A

Cassette mould

49
Q

During Microtomy, what size is the tissue cut to for Light Microscopy?

And for EM?

A

1-6uM

60-90nm

50
Q

Why is the tissue placed in warm water?

A

To remove wrinkles

Doesnt melt paraffin

51
Q

Why is alcohol sometimes used with warm water?

A

Replaces more severe wrinkles

52
Q

After taking the slide out of the warm water, what is the slide coated in and why?

A

Saline solution

Helps it adhere to the slide

53
Q

What does Cryrotechiques avoid for speed?

A

Dehydration / Clearing / Embedding

54
Q

What is used during the cryotechnique

At what temp?

A

Cryostat

-20*

55
Q

what can the cryostat produce that bad

A

Ice crystals (artefacts)

Make it hard to cut

56
Q

When is Slow freezing (Cryostat) suitable for?

A

Low mag. studies

57
Q

How is Fast Freezing (Cryostat) used?

A

Liquid Nitrogen

Glycerol to reduce tissue damage

58
Q

Whats embedded into tissue which acts like paraffin during the crytostat phase

A

OCT

59
Q

Why is staining done?

A

Create High contrast to allow observations of structures

60
Q

How is the paraffin removed for staining?

A

Xylenes

61
Q

Name the two types of Staining techniques

A

Progressive

Regressive

62
Q

with Progressive staining, what is done?

A

Dye applied

Until desired colour is achieved

DIfficult to control

Frozen sections

63
Q

With Regressive staining, what is done

A

Put in solution for set period

Wash with Acid-alcohol to remove stain

Removal of background staining

Large batches

64
Q

Name a type of Stain which is used for nuclear staining

What colour does it go?

A

Haematoxylin –> Haematein (BLUE)

65
Q

What does Haematoxylin need?

A

Mordant (alluminium potassium)

66
Q

What does Carmine stain?

A

Red for nucleus

67
Q

What type of stain can be used for blood smears?

A

Methylene Blue

68
Q

What does H&E stain?

A

Acidic molecules BLUE

Basic Molecules RED

69
Q

Why is the coverslip placed on?

A

Protect it from artefacts

70
Q

Why is labeling done?

A

To prevent incorrect info being distributed to wrong patients

71
Q

Histochemistry

A

Identifies Chemical components

Produces coloured stain when reacting with chemical group

72
Q

PAS Techniqiue

A

Histochemistry

Stain glycogen /glycoproteins

High Background

73
Q

Feulgen Technique

A

DNA red

74
Q

Acridine Orange

A

DNA green

RNA orange

75
Q

Von Kossa

A

Show Calficiation

76
Q

Alcian Blue

A

MC granules

77
Q

Sudan Black

A

Phospholipids Black

78
Q

How is Peroxidase identified?

A

Incubate tiisue with DAB + H202

Produces DARK BROWN in presence

79
Q

How is Acid Phosphotase identified

A

Gomori Method

Formalin + SG + Lead nitrate

Black precipitate

80
Q

what can immunohistochemistry detect?

A

Proteins / carbs / membrane antigens

81
Q

Name the two methods of immunohistochemistry

A

Direct (Antigen + labelled antibody)

Indirect (Antigen + secondary labelled antibody)

82
Q

Positive Control

A

If control fails, experiment is wrong

Shows if techniques are working

83
Q

Negative Control

A

Tests for no false positives

Test specificity of the reaction

Pathobiology (13 decks)

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