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Histopathology Laboratory > Week 4: Fixations > Flashcards

Week 4: Fixations Flashcards

1
Q

This is done to
prevent the decomposition and drying
of tissue samples so that it can be
processed in the laboratory.

A

Fixation

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2
Q

This process is also considered
the first and most critical step
in histotechnology.

A

Fixation

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3
Q

o Heating (blue flame),
microwaving, cryopreservation
(freeze-drying)

A

Physical fixation

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4
Q 
o Achieved by immersing the 
specimen in a fixative or by 
perfusing the vascular system 
with fixative
o For specialized histochemical 
procedures, fixatives can be 
applied in vapor form
A

Chemical fixation

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5
Q

Fixatives chemically link/add
themselves on to the tissue
giving stability to the protein

A

Additive fixation

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6
Q

Example of additive fixation

A

formalin, mercury, osmium

tetroxide

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7
Q

Example of non-additive fixation

A

acetone, alcohols

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8
Q

Fixation ph

A

6-8

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9
Q

What happens in tissue hypoxia?

A

Lower the pH of the solution

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10
Q

What temperature is sufficient to maintain excellent

morphology of tissues

A

room temperature

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11
Q

What temperature is used for regular tissue processing

A

40°C

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12
Q

What temperature is used for electron microscopy and

some histochemistry

A

0-4°C

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13
Q

What fixative is used for osmolarity?

A

Normal phosphate buffered

saline (PBS)

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14
Q

Concentration of fixative in routine laboratory

A

10% formaldehyde

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15
Q

Concentration of fixative in immune electron microscopy

A

3%
glutaraldehyde, 0.25%
glutaraldehyde

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16
Q

commonly used in

routine laboratory

A

formalin

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17
Q 
Made up of only one 
component substance 
(e.g. Formaldehyde, 
HgCl, acetone, alcohol, 
glutaraldehyde)
A

Simple

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18
Q

Made up of two or more
fixatives which have been
added together

A

Compound

19
Q 
Example: Helly’s solution 
(made up of 
formaldehyde, mercurric 
chloride and potassium 
dichromate, Gendre’s 
fixative (ethyl alcohol, 
formaldehyde, glacial 
acetic acid)
A

Compound

20
Q 
Permits general 
microscopic study of 
tissue structures without 
altering the structural 
pattern and normal (e.g. 
10% formol saline, 
Heidenhain’s Susa)
A

Microanatomical fixatives

21
Q

Preserves specific

elements of the cell

A

Cytological fixatives

22
Q

Failure to arrest early

autolysis of cells

A

Failure to arrest early

autolysis of cells

23
Q

Removal of substance

soluble in fixing agent

A

Wrong choice of fixative

24
Q

Presence of artefact
pigments on tissue
sections

A

Incomplete washing of

fixative

25
Q

Tissues are soft and

feather-like in consistency

A

Incomplete fixatio

26
Q

Loss or inactivation of

enzymes needed for study

A

Wrong choice of fixative

27
Q

Shrinkage and swelling of

cells and tissue structure

A

Over fixation

28
Q

Tissue blocks are brittle

and hard

A

Prolonged fixation

29
Q

is the process of
placing an already fixed tissue in a
second fixative in order

A

Secondary fixation

30
Q 
is a form of 
secondary fixation whereby a 
primarily fixed tissue is placed in 
aqueous solution of 2.5-3% potassium 
dichromate for 24 hours to act as 
mordant for better staining effects and 
to aid in cytologic preservation of 
tissues
A

Post-Chromatization

31
Q 
It is a polymerized form of 
formaldehyde, usually obtained as a 
fine white powder, which 
depolymerizes back to formalin when 
heated
A

Paraformaldehyde

32
Q

It is suitable for paraffin embedding
and sectioning, and also for
immunocytochemical analysis

A

Paraformaldehyde

33
Q

It is a dialdehyde – made up of two

formaldehydes

A

Glutaraldehyde

34
Q

➢ Most frequently used for the fixation
of specimens for electron microscopy
➢ But not good for immunohistochemical
staining

A

Glutaraldehyde

35
Q

10% formal-saline

A

Aldehyde

36
Q

suitable blood films or cell

cultures

A

Methanol

37
Q

very good for
cytologic smears
o Example: PAP smears

A

Alcohols

38
Q

It is excellent for fixing dry and
wet smears, blood smears and
bone marrow tissues

A

100% Methyl Alcohol

39
Q

It is used at concentrations of

70-100%

A

Ethyl Alcohol

40
Q 
It is considered to be the most 
rapid fixative and may be used 
for urgent biopsy specimens for
paraffin processing within 5 
hours
A

Carnoy’s Fixative

41
Q

used

on frozen sections and smears

A

Clarke’s solution

42
Q 
o It can be used for rapid 
diagnosis because it fixes and 
dehydrates at the same time, 
e.g., in the frozen section room
o It is good for preservation of 
glycogen
A

Gendre’s Fixative

43
Q

This is recommended for the
fixing of mucopolysaccharides
and nuclear proteins

A

Newcomer’s Fluid

Histopathology Laboratory (2 decks)

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