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MLT > Histology > Flashcards

Histology Flashcards

1
Q

What is Histology?

A

Study of structure of tissues

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2
Q

What are biopsies?

A

Excision of small tissue sample. Taken during Endoscopy procedures, surgery, or needle core

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3
Q

When specimen arrives, what are the two labels?

A

Patient Info and Specimen type

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4
Q

Tissue specimens arriving in lav may arrive in:

A 
Fixative solution (fixed specimen) or;
In a container with no solution or in physiological saline (unfixed or "fresh")
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5
Q

What is Fixation?

A

Process where tissue/specimen placed in chemical which stops decomposition of tissue, undergoes physical and chemical change.

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6
Q

Actions/Effects of Fixation on Tissue?

A

Preserve tissue as lifelike as possible
Prevent putrefaction and autolysis
Some fixatives help staining of tissue after process
Some fixatives act as mordants
Microorganisms will be fixed (and killed)

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7
Q

What is Putrefaction?

A

Decomposition of tissue due to action of bacteria

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8
Q

What is Formaldehyde?

A

Colourless-gas, soluble in water up to 37-40% by weight

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9
Q

What is B5 Fixative?

A

Sometimes used for lymph nodes and bone marrow biopsies, shows good nuclear detail

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10
Q

Use of Zinc Formalin?

A

Replacement for B5 fixative, lymph nodes and/or bone marrow biopsies. Shows good nuclear detail.

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11
Q

Safety concerns handling with Fixatives?

A

Carcinogenic - sensitive to skin
Fumes - irritate eyes and mucous membrane of nose and throat
Toxic - can be fatal if inhaled or swallowed
Wear PPE, respirator, work in fume hood/ventilation

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12
Q

Grossing of specimen

A

Grossing includes description of tissue, assigned surgical number, surgical procedure, type of tissue received.

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13
Q

What are the different tissue details?

A

Size, colour, consistency, abnormalities.

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14
Q

Labelling cassettes

A

Labelled with surgical number with part number of tissue

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15
Q

What is Decalcification?

A

Controlled removal of calcium from a tissue.

Must be fixed before decalcified or cell morphology will be destroyed

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16
Q

What is Dehydration?

A

Controlled removal of water from tissue.

Needed for water to be replaced with paraffin wax

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17
Q

What is Clearing?

A

Removal of dehydrating agent and replacing with paraffin wax.

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18
Q

What is Infiltration?

A

Removal of clearant and infiltrate tissue with molten paraffin wax.

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19
Q

What is the Paraffin wax process?

A

Where fixative is removed with steps of dehydration, clearing, and wax infiltration.
During embedding process, molten wax will harden to support tissue during microtomy

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20
Q

What is a closed system of Tissue processing?

A

In a closed chamber (retort) and solutions are pumped in retort, in sequence.

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21
Q

What is the Clean or Purge cycle?

A

Must be run immediately after tissue cassettes removed.

Uses xylene then alcohol, xylene removes wax and alcohol removes xylene, ready for next program.

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22
Q

Storage of Chemicals

A

Store in segregated and approved area - flammable cabinet
Keep container in a cool, well ventilated area
Keep containers tightly closed
Avoid all possible sources of ignition

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23
Q

What is Embedding?

A

Tissue placed in mold of liquid (molten) paraffin.

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24
Q

What is Hematoxylin and Eosin (H&E) Staining?

A

Hematoxylin binds to phosphate radicals of DNA and RNA causing nuclei to stain blue. Eosin stains other tissue components (cytoplasm) pink/red

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25
Q

Straining results of RBCs and Nuclei?

A

Red for RBC

Dark blue for Nuclei

26
Q

What is Progressive Staining?

A

Tissue left in dye until sufficient dye as been used and desired intensity of colouring is attained.
Often used for rapid staining of frozen sections for stat diagnosis.

27
Q

Purpose of coverslipping?

A

Protect tissue section.
Store slides for long period of time if resinous media used.
Slide to be viewed and seen in detailed manner under microscrope.
Preserve stain.

28
Q

Types of Resinous Mounting Media.

A

Permount.
Resin, have refractive index close to glass (1.52)
Dissolve in xylene, so slide being mounted must be dehydrated and then cleared (in xylene) before coverslipping

29
Q

What is Pathology?

A

Study of diease

30
Q

What is Histopathology?

A

Study of diseased tissue

31
Q

Purpose of Histopathology department?

A

View processed tissue for malignancy or abnormalities.

Slides prepared viewed under microscope, typically received in surgical lab/ Are Fixed then Grossed.

32
Q

Types of Specimen arrived in Surgical Pathology/Histology Lab?

A 
Removed during surgical procedure, whole part of partial organs, tumors, cysts, biopsies, curettings:
Liver lobe
Gall bladder
Ovary/Prostate
Lymph node
Uterine
Mandible
33
Q

What is an Autopsy?

A

Removal of tissue from dead body to determine cause of death to confirm diagnosis. AKA necroscopy or post mortem

34
Q

Importance of Fixation?

A

Essential first step for histological processing. Tissue from body begins to decompose immediately. If not fixed, should be refrigerated at 4 degrees to slow down decomposition

35
Q

Amount of Fixative solution?

A

10 to 20x volume of specimen.

36
Q

What is Autolysis?

A

Decomposition of tissue due to actions of enzymes

37
Q

What is Putrefication?

A

Decomposition of tissue due to action of bacteria

38
Q

Universal Fixative?

A

Formalin

39
Q

10% Neutral Buffered Formalin consist of what % Formaldehyde solution?

A

3.7-4%

40
Q

Function of Formaldehyde?

A

Fixes tissue by cross-linking the proteins.
Relative cheap fixative
Phosphate buffer added to achieve neutral pH

41
Q

What element does B5 Fixative leave during staining?

A

Mercury

42
Q

Gluteraldehyde as a fixative solution

A

Common fixative used for EM. Fixes and tissue cross-links proteins. Penetrates tissue more slowly than formalin, so should have small pieces.

43
Q

Why are small samples wrapped in lens paper or placed in between sponges then into the cassettes?

A

Prevent small samples from escaping cassette.

44
Q

What does “Toto” mean?

A

This means the whole specimen is placed in the cassette for processing.

45
Q

What is the tissue cassettes made of and its purpose?

A

Special plastic polymer which resist most histological solvents. Hold tissue during processing, grossed tissue placed in tissue cassette and a closed lid.

46
Q

Labeling cassettes utilizes?

A

solvent resistant labeller or suitable pencil. Ink and pens will be removed. Some labs use bar code labeling on cassettes.

47
Q

Use of colour code to indicate?

A

Type of fixation on specimen
Priority of spicmen
Biopsy vs. Larger specimen

48
Q

A good decalcifying solution must have:

A

Completely removed calcium salts
Minimize cell damage
Not affect the staining of tissue
Work in a reasonable amount of time

49
Q

Timing for decalcification will vary depending on tissue:

A

Tissue density and temperature. Gentle heat and mild agitation decreases decalcification.
Over decalcification causes tissue distortion and poor staining

50
Q

Different decalcifying solutions are:

A

Acids such as nitric acid, formic acid
EDTA - chelates Ca ions from tissue and binds to them itself - gentle on tissue, but slow (2-3 weeks) and is expensive
RDO - commercial prepared acid solutions

51
Q

Dehydration process involves increasing or decreasing alcohol solutions?

A

Increasing to 100%, prevent distortion of the tissue - Ethanol is the most common

52
Q

Type of clearing agent and it’s properties?

A

Xylene and toluene - must be miscible with both dehydrating agent and with paraffin wax. Removes ethanol and makes tissue more transparent.

53
Q

Ideal temperature for infiltration to melt wax?

A

From 54-58 degrees, during infiltration temperature must be kept a few degrees above melting point of wax.

54
Q

Open System process?

A

Placed in a basket which moves from one solution to next

55
Q

Purpose of embedding?

A

Paraffin cools and hardens so tissue is supported in block of paraffin, the block is removed from embedding mold. Block supports tissue and gives suitable constituency for microtomy.

56
Q

What is Microtomy?

A

Instrument used to accurately cut thin sections of tissue. During microtomy, tissue blocks are trimmed to remove excess wax wax and expose full cross-section of tissue. This is called trimming. Then placed in a water bath 40-45 degrees to remove any wrinkles. Slides are then dried in oven 60 to 65 degrees.

57
Q

H&E Stain for cytoplasm and muscle fibres is what colour?

A

Pink

58
Q

Staining result for Nuclei and RBCs?

A

Nuclei is dark blue

RBC is red

59
Q

What is Regressive Staining?

A

Tissue is over stained and excess dye is removed selectively until desired intensity. The selective removal of excess stain is called differentiation. Most common in histology lab. Takes longer than progressive mode and acid alcohol solution is used as a differentiator.

60
Q

Aqueous Mounting Media is?

A

Glycerol or gelatin based moutants.
Slides are mounted from water or aqueous solution. Used for certain stains where dehydrating solutions such as alcohol cannot be used.
Slides mounted are not permanent and if slide is kept for a long time, edges of coverslip needs to be sealed.

61
Q

Method of manual coverslipping

A
  1. Drop mount media to slide then a coverslip placed on top.

2. Drop mount media on coverslip then slide with tissue section on top of it.

62
Q

Routine Specimen

A 
Accessioning
Fixation
Decalcification (if required)
Grossing
Dehydration
Clearing
Infiltration 
Embedding
Microtomy
Staining
Microscopic examintion

MLT (4 decks)

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