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Pathobiology > Tissue Processing > Flashcards

Tissue Processing Flashcards

(83 cards)

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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
Name 2 advantages of Glutaraldehyde
Quicker than Formalin Preerves intracellular organelles by inactivating all enzymes
26
Name 3 disadvantages of Glutaraldehyde
Penetration slower than Formalin Difficult to remove--> Bad for immunohistochem Inactivated all enzymes not good for EHC
27
Name a fixative useful for histochemisitry
Alcohols (Methanol/Ethanol)
28
What do Alcohol fixatives acheive? *(mechanism)
Denature proteins by removing water/replace with alcohol Alteries tertiary shape but preserves chemical reactivitiy
29
When are Alcohol fixatives used
Histochemistry Fixing smears
30
Name a oxidising agent fixative
Osmium tetraoxide
31
How do oxidising agents work as a fixative
Extensive denaturation of proteins Stablizies lipids
32
When are oxidising agents used? Whats a benefit
Lipid Preservation Poor pentration/Dangerous for cornea
33
Mercuric Chloride
Zenker fluid SH cross linking Not good for ultra structures Toxic Produces black precipitate needs iodine
34
When are Mercuric Chlorides used?
Nuclear / cytoplasmic staining
35
Why is Decalcification done? Name a disease which the stage of decalcification can help towards
Examining minearlised tissues Hydroxyapatite present Osteosarcoma
36
Name a decalficiation agent
Formic acid EDTA
37
Whats the benefit of using Chelating agents during decalcification? Whats the downside
No damage to tissue Takes a long time
38
Why is dehydration done?
Water removed so paraffin can infiltrate tissue
39
Whats the solution for dehydration consist of?
75% ethanol 25% PBS
40
Why is Clearing done?
Removal of alcohol As its MISCIBLE with the paraffin
41
Name the most common clearing agent
Xylene
42
When is Histo-clear used as a clearing agent?
Fine line tissue
43
What does Wax infusion involve?
2-4 baths of Molten paraffin wax (55-60*) for several hours
44
Why is embedding done?
Embeds tissue in support media for structural support
45
Describe 2 features of paraffin
Long chain hydrocarbon Similar hardness to tissue once impregnated into tissue
46
Why is paraffin used?
Easier cutting Structural support Stored Indefinitely
47
When Would plastic/resin be used as a wax?
Thinner sections can be cut As it provides stronger support as its harder
48
Name a type of embedding mould
Cassette mould
49
During Microtomy, what size is the tissue cut to for Light Microscopy? And for EM?
1-6uM 60-90nm
50
Why is the tissue placed in warm water?
To remove wrinkles Doesnt melt paraffin
51
Why is alcohol sometimes used with warm water?
Replaces more severe wrinkles
52
After taking the slide out of the warm water, what is the slide coated in and why?
Saline solution Helps it adhere to the slide
53
What does Cryrotechiques avoid for speed?
Dehydration / Clearing / Embedding
54
What is used during the cryotechnique At what temp?
Cryostat -20*
55
what can the cryostat produce that bad
Ice crystals (artefacts) Make it hard to cut
56
When is Slow freezing (Cryostat) suitable for?
Low mag. studies
57
How is Fast Freezing (Cryostat) used?
Liquid Nitrogen Glycerol to reduce tissue damage
58
Whats embedded into tissue which acts like paraffin during the crytostat phase
OCT
59
Why is staining done?
Create High contrast to allow observations of structures
60
How is the paraffin removed for staining?
Xylenes
61
Name the two types of Staining techniques
Progressive Regressive
62
with Progressive staining, what is done?
Dye applied Until desired colour is achieved DIfficult to control Frozen sections
63
With Regressive staining, what is done
Put in solution for set period Wash with Acid-alcohol to remove stain Removal of background staining Large batches
64
Name a type of Stain which is used for nuclear staining What colour does it go?
Haematoxylin --> Haematein (BLUE)
65
What does Haematoxylin need?
Mordant (alluminium potassium)
66
What does Carmine stain?
Red for nucleus
67
What type of stain can be used for blood smears?
Methylene Blue
68
What does H&E stain?
Acidic molecules BLUE Basic Molecules RED
69
Why is the coverslip placed on?
Protect it from artefacts
70
Why is labeling done?
To prevent incorrect info being distributed to wrong patients
71
Histochemistry
Identifies Chemical components Produces coloured stain when reacting with chemical group
72
PAS Techniqiue
Histochemistry Stain glycogen /glycoproteins High Background
73
Feulgen Technique
DNA red
74
Acridine Orange
DNA green RNA orange
75
Von Kossa
Show Calficiation
76
Alcian Blue
MC granules
77
Sudan Black
Phospholipids Black
78
How is Peroxidase identified?
Incubate tiisue with DAB + H202 Produces DARK BROWN in presence
79
How is Acid Phosphotase identified
Gomori Method Formalin + SG + Lead nitrate Black precipitate
80
what can immunohistochemistry detect?
Proteins / carbs / membrane antigens
81
Name the two methods of immunohistochemistry
Direct (Antigen + labelled antibody) Indirect (Antigen + secondary labelled antibody)
82
Positive Control
If control fails, experiment is wrong Shows if techniques are working
83
Negative Control
Tests for no false positives Test specificity of the reaction

Pathobiology (13 decks)

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