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Histology II sem 2 2019 > Lecture 3: Tissue processing, de-cal > Flashcards

Lecture 3: Tissue processing, de-cal Flashcards

1
Q
  1. Define tissue processing
A

The process of preparing tissue by embedding it in a solid medium for support and rigidity to enable thin sections to be cut.

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2
Q
  1. What is the main aim of tissue processing
A

To provide adequate support to the specimen for microtomy

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3
Q
  1. Give 3 pre-requisites of tissue processing
A
  1. Tissue sample must be well fixed
  2. Tissue sample must be of a suitable size for processing
  3. Fragile, Friable and Minute fragments must be securede.g.: by wrapping in foam pads.
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4
Q
  1. Describe a method used for small tissue for ensuring no tissue is lost during processing
A

Use of a foam pad which goes inside the cassette

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5
Q
  1. List the 4 major steps in tissue processing in order
A

1.

  1. Dehydrating
  2. Clearing
  3. Wax Infiltration or Impregnation
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6
Q
  1. List 4 factors that affect processing
A
  1. Type of tissue
  2. The reagents used
  3. Agitation
  4. Heat
  5. Vacuum
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7
Q
  1. List the main reagents used in TP
A

The reagents used..

Dependent on type of investigation.

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8
Q
  1. How does agitation and heat affect TP
A

Agitation

  • Provides fluid access from all directions.
  • Enabling faster and more effective processing
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9
Q
  1. Define dehydration
A

Process which displaces the residual fixative as well as cellular water (free not bound).

At the lower end of the ethanol concentrations, water soluble proteins are removed, whilst towards the 100% ethanol step, certain lipids are dissolved.

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10
Q
  1. What is the purpose of using gradient alcohol in TP
A

Graded alcohols are used in dehydration to remove free water and keep the bound water in place, as well as to not shock the tissue causing dry and brittle tissue or artifacts

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11
Q
  1. Give 2 types of dehydrating agents + adv disadv
A

Ethanol

  • hydrophilic i.e.. miscible with water
  • however: dissolves lipid; flammable

Iso-propyl alcohol

  • xylene free processing
  • Irritant, Flammable
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12
Q

Dehydrating agents must meet what four criteria?

A

Must :

  1. Replace fixative completely
  2. Be miscible with fixative reagent
  3. Not compromise tissue integrity
  4. Not interfere with subsequent processing step
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13
Q
  1. Define clearing
A

Tissue processing step that removes the dehydrant from tissue in preparation for infiltration (De-alcoholization)

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14
Q
  1. Give advantages and disadvantages of 3 types of clearing agents
A

Xylene

Most common-cost effective, does not interfere with staining

Causes irritation, toxic, flammable, tissue damage –long term

Chloroform

-slow acting

Causes irritation, toxic-health hazard, causes sectioning difficulty

Toluene

-good tissue structure preservation

Not ideal for routine use-more toxic and more expensive than xylene

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15
Q
  1. Most common type of infiltrating agent
A

Paraffin Wax

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16
Q
  1. What is the main advantage of using paraffin wax in preparing tissue for embedding
A
  • Wax assists in preparing tissue for embedding
  • Wax creates stability and rigidity in the tissue ->ready for microtomy
17
Q
  1. 3 advantages of using paraffin wax
A
  • Blocks are easy to prepare in large numbers
  • Easy to store
  • Easy to cut relatively thin sections
  • Relatively safe to handle
  • In-expensive compared to other agents
  • Method is simple
  • Allows automation and batch processing
18
Q
  1. What is the main disadvantage of using celloidin as an impregnating agent
A
  • Slow process-Undesirable
  • Once celloidin has hardened and the blocks trimmed, they must be stored in 70% alcohol to prevent drying out.
  • Sections not as thin as paraffin
19
Q
  1. Give one use of resin as infiltrating agent
A

Epoxy resin-most commonly –EM studies

20
Q
  1. Define de-calcification
A

Decalcification-is removing calcium salts from bone or other calcified tissue so that good-quality paraffin sections can be prepared without compromising tissue integrity.

21
Q
  1. List method of improving efficiency of tissue in the process of decal
A
22
Q
  1. List 3 ways in which decal can be achieved by
A

-

23
Q
  1. Give 2 properties of a good decal
A

-

24
Q
  1. 2 examples of a strong acid decal
A
  • Nitric acid
  • Hydrochloric acid
25
Q
  1. 2 examples of a weak decal
A

Formic acid

Acetic acid

26
Q
  1. 1 advantage/disadvantage of chelating agent (EDTA)
A

Slow process days –> months

Is also used as a surface Decalcifier for paraffin tissue with Calcium is present

27
Q
  1. Duration of decal is dependent on
A
28
Q
  1. 1 dis/advantage of using a strong acid as a decal
A

-

29
Q
  1. What Is the effect of the following – concentration, temperature, agitation, fluid access
A

-

30
Q
  1. List 3 ways to determine the end-point of decal
A

-

Histology II sem 2 2019 (6 decks)

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