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3rd Year > fixation > Flashcards

fixation Flashcards

1
Q

First and most critical step in HTP

A

fixation

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2
Q

process that preserves tissues from decay, thereby preventing autolysis or putrefaction

A

fixation

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3
Q

improves ____ makes cell ___ to the effects of chemicals used in processing and improves ___ ___

A

staining, resistant, microscopic examination

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4
Q

fixatives employed prevent autolysis by inactivating ___ enzymes

A

lysosomal

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5
Q

fixatives have ___ effect that protect tissue from pathogen

A

bactericidal

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6
Q

Primary goal of fixation

A

preserve the morphologic and chemical integrity of the cells

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7
Q

second goal

A

to harden and protect tissue from the trauma so that it is easier to cut and process for microscopy

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8
Q

Fixation can be done using chemical solutions known as ___

A

fixatives

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9
Q

physical methods include:

A

eating, microwaving, cryo-preservation, freezants such as liquified CO2 or liquified nitrogen or freon gas

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10
Q

CO2 fixes at what temperature?

A

-7C

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11
Q

Liquid nitrogen

A

-180C

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12
Q

freon

A

-20C

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13
Q

Specimens should be transferred to fixative quickly <__ hour after surgery?

A

1

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14
Q

volume of solution : specimen

A

20:1 or 10:1

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15
Q

prolonged fixation may result in loss of ____ ____

A

immunohistochemical antigenicity

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16
Q

main factors involved in fixation

volume

A

20:1 - fixative volume to tissue

17
Q

main factors involved in fixation

hydrogen ion concentration

A

best if in 6-8 level

18
Q

common buffer

A

phosphate or bicarbonate

19
Q

factor in fixation

thickness of section

  1. EM = __ - __mm
  2. LM = __mm
A
  1. 1-2 mm for
  2. 2mm
20
Q

factor in fixation

osmolality

recommended solution

A

isotonic solution

21
Q

factors in fixation

temperature

  1. tissue processors ____C
  2. electron microscopy ____C used for ____
  3. Refrigeration ___C
A
  1. 40C
  2. 0C - 4C, histochemistry
22
Q

factors in fixation

concentration

As ___ as possible concentration of solution

formalin ideal concentration ___
glutaraldehyde concentration ___

A

lowest

10%

3%

23
Q

factors in fixation

duration of fixation

formalin fixation duration - __ hours

formalin is washed out after __ hours

A

2-6 hours

24 hours

24
Q

factors in fixation

time interval

A

.

25
Q

characteristics of a good fixative

A

cheap

stable

safe to handle

kills the cell quickly to minimize distortion of cell constituents

26
Q

characteristics of a good fixative pt.2

A

inhibits bacterial decomposition and autolysis

minimum shrinkage of tissues

permits rapid and even penetration of tissues

hardens tissue for easier cutting

isotonic

makes cellular components soluble to hypotonic solutions

permits subsequent application for staining procedures

27
Q

washing out agents

tap water - used to remove excess ___, ___, and ___

A

chromates, formalin, and osmic acid

28
Q

washing out agents

50-70% alcohol washes out ___

A

picric acid (Bouin’s solution)

29
Q

washing out agents

alcoholic iodine removes excess ___

A

mercuric fixatives

30
Q

failure to arrest early autolysis of cell

A

insufficient fixative

31
Q

removal of substances soluble in fixing agent

A

wrong choice of fixative

32
Q

presence of artifact pigments on tissue section

A

incomplete washing of fixative

33
Q

tissues are soft and feather-like in consistency

A

incomplete fixation

34
Q

loss or inactivation of enzymes

A

wrong choice of fixative

35
Q

shrinkage and swelling of cells and tissue structure

A

overfixation

36
Q

tissue blocks are brittle and hard

A

prolonged fixation

37
Q

fixation artifact

well-known artifact that is produced under acid condition

A

formalin pigment

38
Q

artifact

may be found in surgical specimens particularly in liver. associated with intense eosinophilic staining at the center

A

crush artifact

3rd Year (7 decks)

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