FIXATION Flashcards

1
Q

Post martem devomposition or autolysis occurs due to the action of what enzyme

A

Hydrolytic enzymes

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2
Q

Fixation prevents autolysis by inactivating by what enzyme

A

Lysosomal enzyme

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3
Q

2 types of mechanism

A

Additive fixation

Non additive fixation

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4
Q

Mechanism whereby the chemical constituent of the the fixative is taken in

Forming crosslinks or molecular complexes

A

Additive fixation

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5
Q

Mechanism whereby altering the tissue composition

Upon removal of water to to hbonds, new cross links are established

Acetone and alcohon fixatives are examples

A

Non-Additive fixation

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6
Q

Formalin heated at 60C

A

Rapid fixation for very urgent biopsy specimens

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7
Q

Formalin heated at 100C

A

For tuberculosis

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8
Q

Volume of fixative used

A

10-25 times the volume of the tissus

Maximum effectiveness
- 20 times the volume of specimen

For museum
- not less than 50-100 times the specime

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9
Q

Penetration of fixatives in the tissue at the rate of

A

1mm/hour

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10
Q

Intensifies hematoxylin staining?

Inhibits?

A

Formaldehyde

Osmium tetroxide

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11
Q

Fixative that react with viruses

A

Mercuric chloride

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12
Q

Commonly used fixatives for nucleic acids

A

MEC

methanol
Ethanol
Carnoys

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13
Q

Involves thermal coagulation

For frozen tissue sections (urgent biopsies)

Preparation of bacteriologic smear

A

Heat fixation

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14
Q

Process of placing an already fixed tissue in a second fixative

Acting as a mordant

A

Secondary fixation

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15
Q

Stain MASSON’S TRICHROME

A

for connective tissue

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16
Q

MALLORY’s ANILINE BLUE STAIN

A

for collagen

17
Q

PHOSPHOTUNGSTIC ACID HEMATOXYLIN

A

for striated muscles

18
Q

Secondary fixation whereby the primary fixation is placed in Potassium dichromate

A

Post-chromatization

19
Q

Removing of excess fixative in order to improve staining and remove artifacts

A

WASHING-OUT

20
Q

Tap water used to remove

A

COF

chromates
Osmic acid
Formalin

21
Q

Used to remove excess amount of picric acids

A

50-70% alcohol

22
Q

Used to remove excess mercuric chloride

A

Alcoholic iodine

23
Q

Fixation is retarded by

A
Size and thickness
Mucus
Fat
Blood
Cold temp
24
Q

Fixation enhanced by

A

Size and thickness
Agitation
Heat

25
Q

Volume of fixatives if expensive osmium tetroxide is used

A

5-10 times the volumes only

26
Q

Floating of air filled organs like lungs may be avoided

A

Covered with several layer of gauze g

27
Q

Before hollow organs like stomach and intestines immersed, do:

A

Packed with cotton soaked fixatives

28
Q

What to do to prevent brain from flattening

A

INTRAVASCULAR PERFUSION

Washing out of bloos with RINGERS LACTATE

29
Q

Hard tissues
-cervix, uterine, fibroids, hyperkeratotic, nails

What u should do? For tissue softener?

A

LENDRUM’S METHOD

Washed out with running water overnight

Add 4% acqueous phenol solution for 1-3 days

30
Q

Factors considered when choosing the right fixatives

A
Need for immediate exami
Tissue structure 
Type of tissue
Type of section 
Staining technique
31
Q

Ideal concentration of glutaraldehyde for EM

A

0.25%

32
Q

Bleaching of tissues can be prevented by

A

Changing of fluid every 3MONTHS

33
Q

Natural color of tissue may be restored tru

A

70% alcohol

34
Q

For glycogen demonstration

A

Picric acid

35
Q

For glycogen preservation

Glycogen polarization

A

Alcohol fixatives

36
Q

Strong oxidizing solution

A

Chromic acid

Osmium tetroxide

37
Q

Stong reducing agents

A

Formaldehyde