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HISTOLOGY > HISTO OVERVIEW > Flashcards

HISTO OVERVIEW Flashcards

1
Q

What is the size specimens need to be?

A

2.5x3.0x0.5mm

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2
Q

What is the use of wax boards?

A

Used to pin something open ex. intestine, trachea, esophagus

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3
Q

What is the use of margins in grossing?

A

Demonstrate how the tissue was in the body, marks proper orientation during embedding

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4
Q

What does magenta indicate in marking margins?

A

It indicates which side to place against the base of the mold

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5
Q

What does white indicate in the marking margins?

A

The last piece of tissue that will cut

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6
Q

What does black indicate in the marking margins?

A

Black indicates the border of the cut, if the infection/abnormality extends beyond the margin, it means more needs to be cut

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7
Q

What are cassettes labelled with?

A
  • Year the sample was taken
  • The method the specimen was obtained i.e. surgical
  • The registration number
  • Specimen designation (a letter)
  • Block number (number of blocks made)
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8
Q

Why is fixation the most important?

A

It prevents post-mortem decomposition as well as preserve the tissue in a life-like manner

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9
Q

What is Putrefaction?

A

Occurs when microorganisms ingest everything, creating pockets of gas (aggressive)

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10
Q

How can autolysis occur?

A

If the tissue is too big/thick, the tissue that was deep never got fixed because it took too long for the fixative to get there

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11
Q

What are the functions of preservation?

A

Prevents desiccation, osmotic swelling and shrinkage, autolysis, putrefaction, solidification of material within cells, hardening of tissues and it fortifies and stabilizes tissues against repeated exposure to reagents

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12
Q

What does optical differentiation do?

A

Fixation alters the refractive index (makes tissue clearer) of different cellular components

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13
Q

What is vapor fixation?

A

Volatile chemicals are used on fresh tissue, tissue does not come in direct contact with solution

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14
Q

What is liquid fixation?

A

Chemicals dissolved into a solvent, chemical then enters the cells by diffusion

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15
Q

What is perfusion?

A

Injecting a liquid fixative into a vein or an artery (avoids layer fixation). Method of choice in fixing a whole brain.

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16
Q

What is the best ratio for fixative to the tissue?

A

15:1 or higher

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17
Q

What is a coagulant fixative?

A

Removes water by altering the structure of the protein

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18
Q

What is a non-coagulant fixative?

A

Adds a chemical factor into the tissue

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19
Q

What is an additive fixative?

A

Adds a chemical factor into the tissue

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20
Q

What is a non-additive fixative?

A

Does not add anything into the tissue

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21
Q

What is a tolerant fixative?

A

A fixative that no matter how long you stay inside the fixative, it will not cause adverse effects

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22
Q

What is an intolerant fixative?

A

A fixative that under too much exposure will cause adverse effects to the tissue

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23
Q

What is 10% Neutral Buffered formalin?

A
  • It is the most widely used fixative, tolerant, non-coagulant, additive fixative
  • Fast penetration rate but it fixes slowly
  • Fixation time is generally kept at 24hrs
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24
Q

What is Glutaraldehyde used for?

A
  • Used only in electron microscopy as a primary fixative as it preserves the ultrastructure, best for morphology
  • Is an additive, non-coagulant and tolerant
  • Has a slow penetration rate and depth (2mm)
  • Tissues should have a maximum fixation time of 2hrs or less
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25
Q

Why is Formalin buffered?

A

So that acid formalin hematin is not produced

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26
Q

What is Acid Formalin Hematin, and how is it removed?

A

It is a pigment that is removed with saturated picric acid, alcohol coats slide evenly and helps remove it uniformly

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27
Q

What is HgCl2 (Zenkers) used for?

A
  • Best fixative for lymph node and renal node biopsies
  • Coagulant fixative, additive (leaves mercury behind, increasing acidophilia + basophilia)
  • Extremely toxic
  • Always produces an artifact
  • Inhibits freezing
  • Is radio opaque
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28
Q

What happens in Dezenkerization?

A

Saturated iodine alcohol removes mercury pigment, iodine combines with Hg and makes it larger/heavier, Sodium thiosulphate removes iodine (clears background)

29
Q

What is zinc formalin?

A
  • Works like HgCl, mainly used as a secondary fixative for BM biopsy
  • Great for lymph nodes as well as IHC studies
  • Maximum fixation time is 2hrs
    -Non-tolerant
30
Q

What is Bouins?

A
  • Contains Picric Acid, Formaldehyde (37-40%), and glacial acetic acid
  • Mainly used as a secondary fixative to enhance trichrome staining by increasing the tissues’ acidophillia
  • Gives brilliant nuclear staining + cytoplasmic staining (b/c of glacial acetic acid)
  • Maximum staining is 24hrs
  • Will lyse RBC and deplete iron stores
31
Q

What is Ethanol?

A
  • Coagulant, simple fixative, intolerant
  • Fixes and dehydrates the specimen at the same time
  • Mainly used with frozen specimens for cell surface antigens in IHC as well as demonstration of enzymes that under routine processing will be lost
32
Q

What is Osmium Tetraoxide?

A

-Lipid fixative (only one)
-Used as a secondary fixative in EM
- Osmium creates an additive complex with lipids rendering the lipids electron-dense and impervious to chemical treatments
- Extremely dangerous
- Will render eyes black if worked outside the fume hood

33
Q

What is calcium stored as in the body?

A

Hydroxyapatite

34
Q

How can calcium be removed?

A
  • Chemically
  • Microincineration
  • Ultrasonics
  • Electrical ionization
  • Ion exchange resins

*Too expensive and take too long in a clinical setting

35
Q

Why is EDTA not used often in decalcification?

A

Takes 6-8 weeks to completely decalcify tissue, takes too long for turnaround time

36
Q

What pH is Calcium soluble at?

A

lower than 4.5 pH

37
Q

How long do strong acids take to decalcify?

A

1-2 days (nitric and hydrochloric acid)

38
Q

How long do weak acids take to decalcify?

A

3-5 days (formic acid)

39
Q

What does the type of acid used for decalcification depend on?

A

Urgency and degree of mineralization

40
Q

What is the best method for end-point testing?

A

X-ray

41
Q

What is the most specific method for end-point testing?

A

Oxalate test

42
Q

Why is Oxalate testing not the best method?

A

This can cause over-decalcification because if calcium remains within the solution it can overshoot it by a day

43
Q

What are the most common physical methods in end-point testing?

A

Poking, prodding and bending

44
Q

What can neutralize tissues after decalcification?

A

Lithium hydroxide or even washing in water for a couple hours

45
Q

Why is neutralization required after decalcification?

A

Makes sure residual acids wont affect processing

46
Q

What are the steps of processing?

A
  1. Dehydration
  2. Clearing
  3. Infiltration
47
Q

What does dehydration involve?

A
  • Ascending grades of ethanol are used to dehydrate tissue (70-80%, 95%-100%)
  • This step removes formalin
  • Multiple solutions help avoid contamination
48
Q

What does dehydration involve?

A
  • Ascending grades of ethanol are used to dehydrate tissue (70-80%, 95%-100%)
  • This step removes formalin
  • Multiple solutions help avoid contamination
49
Q

What does clearing involve?

A
  • Xylol is used as a clearing agent
  • Removes alcohol
50
Q

What are the 3 universal solvents used in Histology?

A

Dioxane, Tertiary Butanol and Tetra Hydrofuran

51
Q

What tissue factors affect processing?

A
  • Size, density and tissue type
52
Q

What chemical factors affect processing?

A
  • Reaction temperature, agitation and vacuum
53
Q

What does infiltration involve?

A
  • Paraffin wax infiltrates the tissue giving it internal support
54
Q

What is the melting point of Paraffin?

A

40-60C b/c greater than 60 denatures proteins

55
Q

What is simple paraffin?

A

It is pure paraffin, derived from petroleum

56
Q

What is additive paraffin?

A

Additives are added to the wax to either make the wax softer or harder than the simple paraffin wax. This includes plastic resins, rubber, beeswax, etc.

57
Q

What is the plastic point?

A

The more plastic a material is the lower its plastic point, higher plastic point means it is less flexiable.

58
Q

What will cause a lack of infiltration and what does it lead to?

A
  • Any alcohol or water left in the tissue
  • Leads to lack of support w/i the tissue, resulting in poor or impossible sectioning
59
Q

How many microns can paraffin be used up to?

A

1 micron

60
Q

What is ultra-processing?

A
  • It is done in EM (70nm)
61
Q

What is the primary and secondary fixative in EM?

A

Primary –Glutaraldehyde
Secondary –Osmium Tetaroxide

62
Q

What does dehydration involve in ultra-processing?

A

It is the same as routine processing

63
Q

What is a transitional fluid used for in ultra-processing?

A

It is required to make the dehydrated tissue miscible with epoxy resin. Propylene oxide is generally used.

64
Q

What does infiltration involve in ultra-processing?

A

Expoxy is used to infiltrate the tissue to give it a harder consistency. Requires a polymerization step, where blocks are baked at 60C overnight, no re-embedding can be done.

65
Q

How many microns is microtomy done at?

A

4-6 microns

66
Q

What are cryostat blades coated with?

A

Teflon

67
Q

What type of blades does EM use?

A
  • Glass/steel wedge knives used for semi-thin sections
  • Diamond blades are used for ultrafine sections (tungsten blades)
68
Q

How does a small clearance angle affect microtomy?

A
  • Sections will be compressed, might have thick and thin and it will be harder to create a ribbon
69
Q

How does a large clearance angle affect microtomy?

A
  • The blade will scrape the tissue rather than cut and creating a ribbon will be difficult

HISTOLOGY (2 decks)

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