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[2S] HP LEC > fixation > Flashcards

fixation Flashcards

1
Q

first step in histotechnology

A

fixation

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2
Q

fixation preserves the biological tissues in a __ manner

A

life-like

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3
Q

purpose of fixation

A

preserve the morphological and chemical integrity while preventing decay

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4
Q

T/F Fixation prevents degeneration, decomposition, and putrefaction of tissues.

A

T

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5
Q

two common specimens submitted to the laboratory for fixation

A

biopsy specimens (surgery) & autopsy specimens (dissection room)

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6
Q

Fixation hardens tissues and prevents ______ and ______ which are destructive processes after cell death

A

autolysis ; putrefaction

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7
Q

maximum recommended thickness for tissue samples submitted for fixation

A

5 mm

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8
Q

T/F Fixation can be skipped if the tissue is being processed immediately after removal.

A

F - Fixation is crucial to preserve tissues, regardless of immediate processing.

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9
Q

t/f in preventing or arrest degenerative processes, putrefaction refers to the disruption of the cell due to lysosome while autolysis refers to the bacterial decomposition

A

f (autolysis, putrefaction)

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10
Q

3 types of physical methods of fixation

A
  • Heat fixation
  • Microwave fixation
  • Cryo-preservation
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11
Q

OOO: Physical method of fixation
A) Heat fixation
B) Cryo-preservation
C) Formalin
D) Microwave fixation

A

C) Formalin – chemical fixative.

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12
Q

3 Chemical Methods of Fixation

A
  • Immersion Fixation & Perfusion Fixation
  • Coagulant fixatives
  • Non-coagulant cross-linking fixative
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13
Q

chemical fixation preserve tissue through chemical processes like ______ or _________

A

immersion fixation or perfusion fixation

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14
Q

Chemical constituent taken into the cell, forming molecular complexes and stabilizing proteins

A

ADDITIVE FIXATION/ NON-COAGULANT FIXATIVES

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15
Q

T/F: Additive fixation involves the incorporation of a chemical fixative into the tissue, forming molecular complexes that stabilize proteins.

A

T

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16
Q

Capable of dehydration/ removing of water molecules for hardening or stabilizing tissue

A

Dehydrant coagulant fixatives

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17
Q

Alteration of tissue composition by removing bound water molecules at Hydrogen bonds within protein molecules

A

NON-ADDITIVE FIXATION /COAGULANT FIXATIVE

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18
Q

remove bound water molecules and stabilize proteins by forming crosslinks within the tissue.

A

non-additive (coagulant) fixatives

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19
Q

non-additive fixation uses coagulant fixatives that alter the tissue composition by removing ________ molecules from protein structures.

A

water

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20
Q

OOO: Additive fixatives
A) Formalin
B) Mercury
C) Alcohol
D) Osmium tetroxide

A

C) Alcohol – dehydrant, not additive fixative

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21
Q

T/F The volume of the fixative is twice the volume of the specimen

A

F (10-20 or 25 times)

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22
Q

BASIC MECHANISM IN FIXATION

Fixing agent is not incorporated into the tissue

A

NON-ADDITIVE FIXATION /COAGULANT FIXATIVE

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23
Q

3 BENEFITS OF FIXATION

A

Hardens tissue for sectioning
Prevents autolysis and putrefaction
Enhances cell avidity for special stains

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24
Q

T/F Fixation improves the tissue’s ability to absorb stains, which is beneficial for microscopy and further examination.

A

T

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25
Q

optimal pH range for fixation is ___

A

6-8

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26
Q

two common buffers used in fixation to maintain an optimal pH range

A

phosphate and bicarbonate

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27
Q

OOO: Commonly used buffer in fixation
A) Cacodylate
B) Veronal
C) Ammonia
D) Bicarbonate

A

Ammonia – not commonly used as buffer

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28
Q

T/F High acidity during fixation can precipitate formalin pigments and cause structural changes that harm the tissue.

A

T

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29
Q

increased temp during fixation increases the rate of ______ and speeds up chemical reactions between the fixative and tissue elements.

A

diffusion

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30
Q

temperature range to carry out fixation for electron microscopy

A

0-4°C

31
Q

T/F: Fixation at cold temperature is standard for most surgical specimens, but temperatures up to room temperature can also be used for further fixation.

A

F - room temp is standard, can be used until up to 40-45°C

32
Q

why is temperature control important during fixation

A

affects the speed of diffusion, rate of chemical reactions, and preservation quality of tissue

33
Q

Fixation at high temperatures (60-65°C) leads to rapid chemical reactions but may also increase tissue _______.

A

Degradation

34
Q

OOO: Affect fixation
A) Temperature
B) Color of the tissue
C) pH
D) Duration of exposure

A

B Tissue color

35
Q

T/F: Chemical reactions during fixation occur more rapidly at higher temperatures, which can speed up the process but may also increase the risk of damaging the tissue.

A

T

36
Q

T/F: The recommended section thickness for electron microscopy is 2 cm square.

A

F (electron microscopy is 1 to 2 mm square; light microscopy is 2 cm square)

37
Q

recommended section thickness for light microscopy

A

2 cm square

38
Q

T/F: A hypertonic solution causes cell swelling and leads to poor fixation.

A

F (hypertonic solutions - cell shrinkage; isotonic and hypotonic solutions - swelling and poor fixation)

39
Q

best results for fixation are usually obtained using slightly ______ solutions, with a concentration of 400-450 mOsm.

A

Hypertonic

40
Q

T/F Formaldehyde is typically used at a concentration of 3% for fixation.

A

False (10% for fixation; glutaraldehyde - 3%)

41
Q

recommended concentration of glutaraldehyde for immunoelectrochemistry

A

0.25%

42
Q

Select all that applies: Effect of prolonged fixation
A) Tissue shrinkage
B) Tissue hardening
C) Increased enzyme activity
D) Inhibited immunological reaction

A

A, B, D (Prolonged fixation inhibits enzyme activity)

43
Q

T/F: Primary fixation in buffered formalin typically lasts 2-6 hours.

A

T

44
Q

Speed is a critical practical consideration in fixation because tissues should be placed in a fixative as soon as they are removed to prevent ______ and ______.

A

Autolysis & putrefaction

45
Q

T/F: rate of penetration for aldehyde fixatives is 1 cm per hour

A

F - 2-3 mm per hr

46
Q

recommended volume of fixative relative to the tissue volume to ensure effective fixation

A

10-25x the volume of the tissue (20x most effective)

47
Q

T/F: The size and shape of the tissue can affect fixation time and penetration, and refrigeration can be used to slow decomposition if immediate fixation is not possible.

A

T

48
Q

tissue size must be kept at around ___ square to ensure proper penetration by the fixative and maintain a fixation time of ____ hrs

A

2 cm square, 4-6 hrs

49
Q

T/F refrigeration is not recommended if tissue cannot be fixed immediately because it accelerates decomposition.

A

F – slows down decomposition if tissue cannot be fixed immediately

50
Q

OOO: Tissue fixation?
A) Tissue hardening
B) Improved ease of sectioning
C) Inhibition of bacterial decomposition
D) Softening of the tissue

A

D) Softening of the tissue – Fixatives harden the tissue, making it easier to handle and section.

51
Q

T/F: Fixation makes soft tissues harder and easier to section, while also increasing infection risks during handlin

A

F - reduces infection risks by inhibiting bacterial decomposition

52
Q

techniques to prevent tissue distortion and improve fixation,

A

a) pinning specimens to a corkboard
b) using a paper/gauze “wick” in tubular structures

53
Q

Prolonged fixation can be difficult to reverse and may cause a loss of _____ in tissues.

A

immunohistochemical antigenicity

54
Q

Select all that applies: Improve the effectiveness of fixation
A) Using fresh fixatives
B) Using a wick in tubular structures
C) Using contaminated fixatives
D) Pinning specimens to a board.

A

A, B, D (contaminated fixatives decrease effectiveness of fixation)

55
Q

fixative made up of only one substance, such as formaldehyde or glutaraldehyde.

A

simple fixative

56
Q
A
57
Q

examples of simple fixatives from the aldehydes category

A

Glutaraldehyde and formaldehyde

58
Q

T/F Mercuric chloride, chromate fixatives, and lead fixative are examples of metallic fixatives under the compound fixative category

A

F – under simple fixative category.

59
Q

OOO: Metallic fixative
A) Mercuric chloride
B) Osmium tetroxide
C) Lead fixative
D) Chromate fixative

A

B) Osmium tetroxide – not metallic

60
Q

distinguishes a compound fixative from a simple fixative

A

compound fixative contains two or more fixatives combined to obtain an optimal effect

61
Q

T/F: 10% Formol saline and Bouin’s solution are examples of microanatomical fixatives.

A

T

62
Q

used for general microscopic study of tissue structures.

A

Microanatomical fixatives

63
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74
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A

[2S] HP LEC (2 decks)

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