fixation

Question 1

First and most critical step in HTP

Answer 1

fixation

Question 2

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

Answer 2

fixation

Question 3

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

Answer 3

staining, resistant, microscopic examination

Question 4

fixatives employed prevent autolysis by inactivating ___ enzymes

Answer 4

lysosomal

Question 5

fixatives have ___ effect that protect tissue from pathogen

Answer 5

bactericidal

Question 6

Primary goal of fixation

Answer 6

preserve the morphologic and chemical integrity of the cells

Question 7

second goal

Answer 7

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

Question 8

Fixation can be done using chemical solutions known as ___

Answer 8

fixatives

Question 9

physical methods include:

Answer 9

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

Question 10

CO2 fixes at what temperature?

Answer 10

-7C

Question 11

Liquid nitrogen

Answer 11

-180C

Question 12

freon

Answer 12

-20C

Question 13

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

Answer 13

1

Question 14

volume of solution : specimen

Answer 14

20:1 or 10:1

Question 15

prolonged fixation may result in loss of ____ ____

Answer 15

immunohistochemical antigenicity

Question 16

main factors involved in fixation

volume

Answer 16

20:1 - fixative volume to tissue

Question 17

main factors involved in fixation

hydrogen ion concentration

Answer 17

best if in 6-8 level

Question 18

common buffer

Answer 18

phosphate or bicarbonate

Question 19

factor in fixation

thickness of section

1. EM = __ - __mm
2. LM = __mm

Answer 19

1. 1-2 mm for
2. 2mm

Question 20

factor in fixation

osmolality

recommended solution

Answer 20

isotonic solution

Question 21

factors in fixation

temperature

1. tissue processors ____C
2. electron microscopy ____C used for ____
3. Refrigeration ___C

Answer 21

1. 40C
2. 0C - 4C, histochemistry

Question 22

factors in fixation

concentration

As ___ as possible concentration of solution

formalin ideal concentration ___
glutaraldehyde concentration ___

Answer 22

lowest

10%

3%

Question 23

factors in fixation

duration of fixation

formalin fixation duration - __ hours

formalin is washed out after __ hours

Answer 23

2-6 hours

24 hours

Question 24

factors in fixation

time interval

Answer 24

.

Question 25

characteristics of a good fixative

Answer 25

cheap stable safe to handle kills the cell quickly to minimize distortion of cell constituents

Question 26

characteristics of a good fixative pt.2

Answer 26

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

Question 27

washing out agents tap water - used to remove excess ___, ___, and ___

Answer 27

chromates, formalin, and osmic acid

Question 28

washing out agents 50-70% alcohol washes out ___

Answer 28

picric acid (Bouin's solution)

Question 29

washing out agents alcoholic iodine removes excess ___

Answer 29

mercuric fixatives

Question 30

failure to arrest early autolysis of cell

Answer 30

insufficient fixative

Question 31

removal of substances soluble in fixing agent

Answer 31

wrong choice of fixative

Question 32

presence of artifact pigments on tissue section

Answer 32

incomplete washing of fixative

Question 33

tissues are soft and feather-like in consistency

Answer 33

incomplete fixation

Question 34

loss or inactivation of enzymes

Answer 34

wrong choice of fixative

Question 35

shrinkage and swelling of cells and tissue structure

Answer 35

overfixation

Question 36

tissue blocks are brittle and hard

Answer 36

prolonged fixation

Question 37

fixation artifact well-known artifact that is produced under acid condition

Answer 37

formalin pigment

Question 38

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

Answer 38

crush artifact