Fixation (Part 1) Flashcards

1
Q

Step in tissue processing that involves preservation

A

FIXATION

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2
Q

Primary goal of fixation

A

To preserve tissues as close to the original as possible

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3
Q

Secondary goal of fixation

A
  • Harden the tissue to facilitate easy cutting (into thin slices)
  • Protect the tissue from trauma of further handling that might be caused by different reagents used in tissue processing
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4
Q

If processing lung specimen (which is thicker than other specimen), the required size is

A

1-2 cm

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5
Q

pH of fixatives

A

should be 6-8

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6
Q

The osmolality of fixative should be

A

Slightly hypertonic but practically, we use isotonic

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7
Q

Hypotonic fixative will cause

A

swelling

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8
Q

Hypetonic fixative will cause

A

Shrinking

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9
Q

Why do we not use concentrated solutions?

A

It will damage the tissue

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10
Q

Maximum effectiveness of fixative

A

20x the volume of the specimen

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11
Q

Ratio of fixative to tissue

A

15-20:1

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12
Q

When do preservation of tissue happens?

A

When the fixative penetrates the tissue

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13
Q

Penetration rate of formalin

A

1mm per hour

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14
Q

few fixatives used for Electron Microscopy; used 5-10x the volume of the specimen

A

Osmium tetroxide

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15
Q

Time and Duration of fixation

A

Should be 24-48 hours

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16
Q

Temperature for manual fixation

A

Room temp

17
Q

Temp for Electro Microscopy and Histochemistry

A

0-4degC

18
Q

Temp for autotechnicon

A

40degC *heat is applied to speed up the process

19
Q

Factors to be considered when using the RIGHT fixative

A
  • Urgency of the case
  • Type of tissue to be processes
  • Tissue structure to be studied
  • Staining technique to be applied
  • Type of section to be made
20
Q

If urgent biopsy, this is used because it is a fast-acting fixative

A

Formalin

21
Q

can be used to preserve brain tissues for the diagnosis of rabies

A

Carnoy’s solution and acetone

22
Q

Cannot be used for kidney specimens

A

Bouin′s solution

23
Q

The routine stain used in Histopath since it is compatible with many fixatives

A

H&E

24
Q

An example of a fixative that can inhibit hematoxylin.

A

Osmium Tetroxide

25
Q

What are the type of section to be made

A

Serial or Individual

26
Q

Factors that will RETARD the fixation (Longer)

A
  • Cold temperature
  • Presence of blood and mucus
  • Size and thickness of the spx
  • Presence of fats
27
Q

The cooler the temperature the __ (shorter/longer) the process

A

Longer

28
Q

Remedy for specimen covered with blood and mucus

A

NSS

29
Q

If the tissue is big/thick, the __ the fixation time

A

Longer

30
Q

Remedy for specimen covered with fats

A

Cut the specimen

31
Q

Factor that will ACCELERATE the fixation process (Shorter)

A
  • Size and thickness of the specimen
  • Apply heat
  • Agitation
32
Q

Range of temperature for fixation process

A

37-56degC (beyond 56degC, tissue would be destroyed)

33
Q

Ensures the rapid entry of fixative to tissue

A

Agitation

34
Q

What is the cause why loss of substance soluble in fixing agents happens?

A

Wrong choice of fixative

35
Q

Incomplete fixation or inadequate fixation will make the specimen __ after fixation

A

Soft

36
Q

Overfixation will make the tissue

A

Too hard