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Histology (MLSCI 250) > Histotechnique > Flashcards

Histotechnique Flashcards

1
Q

Cytology

A

the study of individual cells

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2
Q

Goal of histopathology

A

Preserve tissues in a life-like manner

–> abnormalities can be identified microscopically

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3
Q

Simplified workflow

A

obtain –> fix –> slice –> stain

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4
Q

Reason for fixative solution

A

tissues and cells die/degrade immediately after removal from body
fresh tissues must be transported immediately
placed in fixative solution for transportation

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5
Q

Sources of samples (2)

A

Surgical (biopsy with clean margins)

Post-mortem (autopsy)

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6
Q

Grossing

A

Macroscopic evaluation of specimen

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7
Q

Parameters (5)

A 
Size
Texture
Number/Proportion
Markings
Locations
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8
Q

Fixation

A

Preservation go cells and tissues
Life-like as possible
STABILIZE PROTEIN so it is RESISTANT TO FURTHER CHANGES

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9
Q

Function of Fixatives (4)

A
  1. Prevents putrefaction (rotting) and autolysis (breakdown)
  2. Maintain proper relationships between cells and extracellular substances
  3. Bring out differences in refractive indexes and increase the visibility of/contrast between different tissue elements
  4. Secondary functions: enhance staining, limiting osmotic effects, prevent desiccation
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10
Q

Autolysis

A

Self-destruction after cells death
Caused by Intracellular enzymes
Temperature (warm=more damage)
Specialized cells - more rapid, worse damage
Nuclear changes: pyknosis –> karyorrhexis –> karyolysis
*condensed chromatin –> loose
Cytoplasm: granular and swollen

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11
Q

Putrefaction

A

decomposition by microorganisms

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12
Q

Modes of Action (fixing) (3)

A

Render - inactivate enzymes by stabilizing proteins
Kill - kill bacteria and molds (toxic)
Make - make tissues more receptive to dyes

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13
Q

Impact of Fixing on Tissues (5)

A
  1. Change in size (smaller)
  2. Change in texture (brittle, hard)
  3. Lost material (dissolve lipids)
  4. Chemical alterations (charges and properties may change)
  5. Fixation artefacts (deposits on and around tissues - affect microscopic imagine)
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14
Q

Volume ratio of Fixative/Tissue

A

20/1

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15
Q

T/F: dense tissue is faster to fix

A

FASLE - dense tissues required more time than porous tissues

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16
Q

Fixative Classification (4)

A
  1. Chemical action on proteins
  2. Effect on microscopic appearance of the tissues
  3. Number of fixing reagents in fixative solution
  4. Amount of time tissues can remain in fixative
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17
Q

Chemical action on Proteins:

A

Coagulant - tertiary structure, organelles, mesh
Non-coagulant - cross-linkages (impermeable), insoluble gel (hard to stain)

Additive - combines with protein
Non-additive - changes protein nature, structural configuration or activity

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18
Q

Microscopic appearance of tissue

A
  1. Microanatomical fixative - preserve microarchitecture
  2. Cytological fixative - preserve intracellular structures/inclusions (electron micro)
  3. Histochemical fixative - minimal changes
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19
Q

simple vs compound fixing sequence

A

Simple - 1 fixative

Compound - more than 1 fixative in solution

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20
Q

Tolerant vs intolerant fixing

A

Tolerant - time is flexible

Intolerant - timing is critical

21
Q

Simple Fixatives (8)

A
  1. Formaldehyde and Formalin based fixatives
  2. Glutaraldehyde
  3. Osmium Tetroxide
  4. Potassium Dichromate
  5. Mercuric Chloride
  6. Picric Acid
  7. Ethanol
  8. Acetic Acid
22
Q

Universal Fixative

A

Formaldehyde

23
Q

Formaldehyde

A
24
Q

Formalin-based fixatives

A
25
Q

Glutaraldehyde

A
26
Q

Osmium Tetroxide

A
27
Q

Potassium Dichromate

A
28
Q

Mercric Chloride

A
29
Q

Picric Acid

A
30
Q

Ethanol

A
31
Q

Acetic Acid

A
32
Q

Compound Fixative Formula

A
  1. 1 or more coagulating agent
  2. May contain a non-coagulating agent
  3. always in solution
    4.
33
Q

B-Plus Fixative

A
34
Q

Bouin’s Fixative

A
35
Q

Secondary Fixation

A
36
Q

Formalin Pigment

A
37
Q

How do you remove formalin pigment?

A
38
Q

Mercuty Pigment

A
39
Q

Chrome Pigment

A
40
Q

Goal of Tissue Processing

A
  • remove all water

- replace with an inert, stable material

41
Q

3 steps to remove water

A
  1. Dehydration
  2. Clearing
  3. Infliltration
42
Q

Incomplete dehydration

A

mushy & soft tissue

43
Q

Prolonged dehydration

A

brittle & hard tissue

44
Q

Dehydration

A

slow and gentle

increasing concentrations of alcohol (70%-100%)

45
Q

Clearing

A

Remove dehydrating agent, replace with material miscible with infiltrating agent
Xylene
TOXIC agents

Improper: greasy feel and odor

46
Q

Infiltration

A 
Removal of clearing agent, replaced with intent, stable supportive material
INTERNAL SUPPORT
Long step (vacuum to speed up)
Paraffin wax (with or without additives)
47
Q

Processing Maintenance

A

Replace all single solutions with new
“dirtiest” repeat is replaced and shifted to end position
Occurs after every run

48
Q

Processing Outcomes

A

Tissue shrinkage
Brittle
Lipids dissolved (tightly bound myelin stays)

49
Q

Microwave processing

A

FAST
finicky
1 sample at a time

Histology (MLSCI 250) (18 decks)

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