GPHT LAB - FIXATION Flashcards Preview

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Flashcards in GPHT LAB - FIXATION Deck (57):
1

Makes tissues harder

fixation

2

preserves morphology and chemical constituents of cells and tissues

fixation

3

prevents decomposition and putrefaction of tissues

fixation

4

destroys any microorganisms present in tissue

fixation

5

2 Goals of Fixation

preserves morphology and chemical constituents of cells and tissues
harden the tissues for further processing

6

mechanisms of fixation (2)

additive
non-additive

7

mechanisms of fixation
fixative becomes part of tissue by forming crosslinks or bridges
these bridges stabilize proteins, thus fixing the tissue

additive

8

mechanisms of fixation
fixative does not become part of the tissue
works by removing water present

non-additive

9

ex of additive fixatives

aldehydes, mercury, osmium tetroxide

10

ex of non-additive fixatives

alcoholic fixatives

11

tradition temp of fixation

RT

12

Autotech temp of fixation

40C

13

Rapid fixation

60C

14

What must be the volume of fixative for max effectiveness

20x that of tissue

15

ideal tissue:fixative ratio

1:20

16

ideal fixative:tissue ration

20:1

17

if expensive fixatives are used like osmium tetroxide, what must be the volume

5-10x that of tissue

18

most common fixative, an aldehyde fixative

10% Formalin

19

ratio used in preparing 10% Formalin

1:9

20

how is 10% Formalin prepared

1 part stock solution 37-40% Formalin
9 parts water

21

an aldehyde fixative, addition of phosphate buffer adjusted to pH 7

10% Neutral buffered formalin

22

why is 10% Neutral buffered formalin better than 10% formalin

neutral pH = less chance of developing formalin artifacts

23

disadv of formalin (2)

irritating to nose (rhinitis), eyes (excessive lacrimation), skin (allergic dermatitis)
formalin pigment production

24

brownish pigments due to action of formic acid with blood

formalin pigments

25

brownish pigments w/c can interfere with different processes

formalin pigments

26

formalin pigments happens when tissue sample is ___

bloody

27

an aldehyde fixative whose action is similar with formalin

glutaraldehyde

28

a more pleasing aldehyde fixative because it does not cause irritation

glutaraldehyde

29

disadv of glutaraldehyde

expensive

30

an aldehyde fixative useful for preserving specimen for electron microscopy

glutaraldehyde

31

most common metallic fixative

mercuric chloride

32

metallic fixative very useful to visualize cell detail used in tissue photography

mercuric chloride

33

ex of mercuric chloride fixatives [4]

Zenker's
Zenker's Formol
B5 Fixative
Heidenhain Susa

34

a mercuric chloride fixative for bone marrow

B5 Fixative

35

a mercuric chloride fixative for skin tumor biopsy

Heidenhain Susa

36

disadv of mercuric chloride

tends to form black granular deposits except in Heidenhain Susa

37

all mercuric chloride fixatives tends to form black granular deposits except in ______

Heidenhain Susa

38

black granular deposits are removed using __

iodine

39

metallic fixative for preserving cho
Strong oxidizing agents

chromic fixatives

40

metallic fixative for acid mucopolysaccharides

lead fixatives

41

used in preserving glycogen and embryos

picric acid fixatives

42

disadv of picric acid fixatives

1) yellowing of tissues
2) explosive when dry

43

metallic fixative that must be used wet or in solution

picric acid fixatives

44

ex of picric acid fixatives

Bouin's
Brasil's

45

fixative for nucleoproteins
usually added to nuclear fixatives

glacial acetic acid

46

fixative not suitable for cytoplasmic fixation because cells will swell and burst

glacial acetic acid

47

2 purposes of alcoholic fixatives

fixative
dehydrating agent

48

ex. of alcoholic fixatives

ethanol
methanol
isopropyl alcohol

49

most rapid fixative (among all types of fixative)

Carnoy's

50

fixative used at ice-cold temperatures to preserve enzymes

acetone

51

fixative used for brain tissues for Rabies diagnosis

Acetone

52

fixative and decalcifying agent

trichloroacetic acid

53

2 main uses of osmium tetroxide or osmic acid

fix and stain fats permanently
fixative for EM

54

disadv of osmium tetroxide or osmic acid

expensive
not for routine histopath
corneal blindness

55

why osmium tetroxide or osmic acid not for routine histopath

inhibits hematoxylin, a common stain

56

ex of osmium tetroxide or osmic acid

Flemming's Fixative

57

type of fixation for bacteriologic smears

heat fixation

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