GPHT LAB - FIXATION Flashcards Preview

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Flashcards in GPHT LAB - FIXATION Deck (57)
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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

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