Fixation (Part 1)

Question 1

Step in tissue processing that involves preservation

Answer 1

FIXATION

Question 2

Primary goal of fixation

Answer 2

To preserve tissues as close to the original as possible

Question 3

Secondary goal of fixation

Answer 3

• 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

Question 4

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

Answer 4

1-2 cm

Question 5

pH of fixatives

Answer 5

should be 6-8

Question 6

The osmolality of fixative should be

Answer 6

Slightly hypertonic but practically, we use isotonic

Question 7

Hypotonic fixative will cause

Answer 7

swelling

Question 8

Hypetonic fixative will cause

Answer 8

Shrinking

Question 9

Why do we not use concentrated solutions?

Answer 9

It will damage the tissue

Question 10

Maximum effectiveness of fixative

Answer 10

20x the volume of the specimen

Question 11

Ratio of fixative to tissue

Answer 11

15-20:1

Question 12

When do preservation of tissue happens?

Answer 12

When the fixative penetrates the tissue

Question 13

Penetration rate of formalin

Answer 13

1mm per hour

Question 14

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

Answer 14

Osmium tetroxide

Question 15

Time and Duration of fixation

Answer 15

Should be 24-48 hours

Question 16

Temperature for manual fixation

Answer 16

Room temp

Question 17

Temp for Electro Microscopy and Histochemistry

Answer 17

0-4degC

Question 18

Temp for autotechnicon

Answer 18

40degC *heat is applied to speed up the process

Question 19

Factors to be considered when using the RIGHT fixative

Answer 19

• 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

Question 20

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

Answer 20

Formalin

Question 21

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

Answer 21

Carnoy’s solution and acetone

Question 22

Cannot be used for kidney specimens

Answer 22

Bouin′s solution

Question 23

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

Answer 23

H&E

Question 24

An example of a fixative that can inhibit hematoxylin.

Answer 24

Osmium Tetroxide

Question 25

What are the type of section to be made

Answer 25

Serial or Individual

Question 26

Factors that will RETARD the fixation (Longer)

Answer 26

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

Question 27

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

Answer 27

Longer

Question 28

Remedy for specimen covered with blood and mucus

Answer 28

NSS

Question 29

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

Answer 29

Longer

Question 30

Remedy for specimen covered with fats

Answer 30

Cut the specimen

Question 31

Factor that will ACCELERATE the fixation process (Shorter)

Answer 31

• Size and thickness of the specimen
• Apply heat
• Agitation

Question 32

Range of temperature for fixation process

Answer 32

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

Question 33

Ensures the rapid entry of fixative to tissue

Answer 33

Agitation

Question 34

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

Answer 34

Wrong choice of fixative

Question 35

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

Answer 35

Soft

Question 36

Overfixation will make the tissue

Answer 36

Too hard