dehydration and clearing

Question 1

process of removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation

Answer 1

dehydration

Question 2

removal of water by evaporation from solid, semi-solid, or liquid state

Answer 2

drying

Question 3

10% formalin and Bouin’s

1) 70% - 100& alcohol III = __ - __ hours

2) xylol I = __ - __ hours

3) xylol II = __ hour

Answer 3

1) 3-12 hours

2) 1-2 hours

3) 1 hour

Question 4

characteristics of an ideal dehydrating agent

Answer 4

1. should dehydrate rapidly without shrinkage or distortion of tissue
2. should not evaporate very fast
3. should be able to dehydrate even fatty tissue
4. should not harden tissues excessively
5. should not remove stains
6. should not be toxic to the body
7. should not be a fire hazard

Question 5

commonly used dehydrating agents

Answer 5

alcohol - most commonly used
acetone
dioxane
cellosolve
triethyl phosphate
tetrahydrofuran

Question 6

____ ____is the recommended dehydrating agent for routine dehydration. considered to be the best dehydrating agent because it is ___ ___.

Answer 6

ethyl alcohol, fast-acting

Question 7

___ toxic dehydrating agent, primarily employed for blood and tissue films and for smear preparation

Answer 7

methyl alcohol

Question 8

___ is a slow dehydrating agent, produce less shrinkage and hardening than ethyl alcohol. recommended for tissues that do not require rapid processing

Answer 8

butyl alcohol

Question 9

___ is a cheap dehydrating agent utilized for urgent biopsies which dehydrate in 1/2 to 2 hours. It is a clear, colorless fluid that mixes with water, ethanol, and most organic solvents

Answer 9

acetone

Question 10

___ is a excellent dehydrating and clearing agent that is readily miscible in water, melted paraffin, alcohol, and xylol.it produces less tissue shrinkage than alcohol. however, it is extremely dangerous

Answer 10

dioxane

Question 11

___ dehydrates rapidly. tissues may be transferred from water or saline directly to cellosolve and stored for months without producing hardening or distortion.

Answer 11

cellosolve

Question 12

___ removes water readily and produce very little distortion and hardening of tissue

Answer 12

triethyl phosphate

Question 13

___ reagent that both dehydrates and clears tissue since it is miscible in both water and paraffin.

Answer 13

tetrahydrofuran

Question 14

two types of clearing agents: ___ and ___

Answer 14

organic solvents and oils

Question 15

___ clearing of choice

Answer 15

xylol

Question 16

characteristics of a good clearing agent

Answer 16

should be miscble with alchol
should be miscible with paraffin wax
should not produce excessive shrinkage, hardening, or damage of tissue
should not dissolve out aniline dyes
should not evaporate quickly in a water bath
should make tissues transparent

Question 17

__ most commonly used in histology laboratories. clearing time is usually __ - __ hour/s. used for clearing, embedding, and mounting procedures.

Answer 17

xylene, 1/2 - 1 hour

Question 18

___ is used as an substitute for xylne or benzene for clearing both during embedding and mounting process. time recommended for clearing is __ - __ hours

Answer 18

toluene. 1-2 hours

Question 19

__ preferred by some since it penetrates and clear tissues rapidly. recommended for urgent biopsies and routine purposes

Answer 19

benzene

Question 20

___ is slower than xylene but causes less brittleness. thicker tissue blocks can be processed. used when tough tissues like skin, fibroid, and decalcified tissues.

Answer 20

chloroform

Question 21

___ used to clear both paraffin and celloidin sections. recommended for CNS tissues and cytological studies particularly smooth muscles and skin. clearing is usually complete in __ - __ days

Answer 21

cedarwood oil, 2-3 days

Question 22

not normally utilized but is recommended for embryos, insects and delicate specimens due to its ability to clear 70% alcohol without excessive tissue shrinkage and hardening.

Answer 22

aniline oil

Question 23

__ quality is not guaranteed due to tendency to become adulterated.

Answer 23

clove oil

Question 24

similar to chloroform but cheaper. dangerous to inhale on prolonged exposure

Answer 24

carbon tetrachloride

Question 25

slow acting clearing agent that can be used when double embedding techniques are required

Answer 25

methyl benzoate and methyl salicylate