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MEDI > Foundations of Anatomical Pathology (W9) > Flashcards

Foundations of Anatomical Pathology (W9) Flashcards

1
Q

what are the 3 main functions of the Anatomical pathology Laboratory

A
  • Diagnosis - surgical pathology, cytology, morbid anatomy
  • Teaching - undergraduate, postgraduate
  • Research- cellular and molecular pathology, epidemiology and pathogenesis of disease
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2
Q

define histopathology

A

the microscopic examination of tissue to determine the cause of disease
- can see inflammatory-infectious disease, if something is autoimmune or acquired, and if it is benign or malignant

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3
Q

what are the roles of a medical scientist doing histopathology (3)

A
  • responsible for processing tissue sample
  • preparing specimen to look at under microscope
  • apply techniques (chemical, technical, molecular) to permit accurate microscopic interpretation
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4
Q

describe the steps in routine histopathology

A
  • specimen provided by surgical procedure
  • preserve tissue (fixation) - put into formaldehyde
    straight away (in surgery)
  • process tissue - now in lab the water is removed
  • Microtomy - this section of tissue is removed
  • staining
  • microscopy - dictate the report/outcome
  • report - then determine patient management
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5
Q

what are the 2 types of biopsy that can be taken for skin samples

A

punch biopsy - can be done by a gp to remove something small

wedge biopsy - larger area, shows where it ends

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6
Q

what must be done during specimen reception and dissection

A
  • check that the name of the form is the same as on the specimen jar
  • each are given a unique laboratory number and then are separated
  • biopsies are transferred into cassette.
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7
Q

what is the universal stain

A

Haematoxylin and Eosin (H+E)

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8
Q

are all samples handled the same way

A

no, each sample has a specific protocol for handling it

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9
Q

what cells make up cytology samples

A

cells in body fluids, cells collected by a range of measures

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10
Q

what are 3 categories and some examples the hazards of working in a Histopathology Lab

A
  • Chemical : fixatives, stains, chemicals
  • Physical : sharps, radiation
  • Biological : cross infection
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11
Q

what are some things that can be put in place as protection in an anatomical pathology lab

A
  • appropriately dress and safety wear
  • laboratory design
  • alertness
  • compliance with health and safety guidelines and code of conduct
  • adopt prescribed procedures (to avoid clerical errors, contamination, to ensure patient safety and laboratory integrity)
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12
Q

ethics in Histopathology

A

it is required for all human investigation (discipline and research focused)

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13
Q

define confidentiality in histopathology

A

non disclosure of private health information to an unauthorised person

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14
Q

what is the code of conduct for histopathology

A

health worker are required to provide a safe, high quality, sustainable healthcare system for all of WA.
which includes:
- collaboration
- openness
- respect
- empowerment

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15
Q

what are 3 types of cell degradation that we want to avoid with a tissue specimen

A

Anoxia - restricted blood supply
Autolysis - release of lytic enzymes to self digest
Putrefaction - bacterial contamination

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16
Q

what are 2 type of fixation and an example of each

A

physical - eg. heat fixing bacteria, or microwave radiation of a tissue

chemical immersion - tissue fixation for microscopy

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17
Q

what are 8 outcomes from using fixation processes on a sample
(LSABICHA)

A
  • it is permanently preserved in a life like state
  • stabilizes tissue to allow for further treatment
  • arrests autolysis
  • prevents bacterial decomposition
  • inactivates infections agents
  • minimises loss of soluble cytoplasmic components
  • hardens tissue
  • enhanced avidity for dyes
18
Q

what are 7 factors that affect fixation

A
  • Temperature
  • pH (usually best at 6-8)
  • Osmolarity
  • Penetration ability of fixative
  • Size of specimen (small/thin)
  • Concentration
  • Duration
19
Q

when would cold fixation be used

A
  • if the results are needed asap (while performing a surgery)
  • it is injected with liquid nitrogen
20
Q

what are 6 characteristics of an ideal fixative
(EPASSC)

A
  • economic
  • preserves in a life like state
  • will not add artifact material to the tissue
  • will no swell or shrink tissue
  • will be safe for user and environment
  • convenient shelf life and storage
21
Q

what are the structures in a cell that require stabilization (6)

A
  • lipoproteins of the cell membrane
  • cytoskeleton fibrous proteins
  • fibrous glycoproteins
  • globular proteins of the cytoplasm and extracellular fluid
  • mucosubstances
  • nucleic acid
22
Q

what are 4 types of chemical fixatives and an example of each

A
  • aldehydes : formaldehyde
  • oxidising agents : potassium dichromate
  • protein coagulants : ethanol, methanol
  • uncertain mechanism : picric acid
23
Q

what are the 2 common aldehydes used in fixation and what are they used for

A

formaldehyde - routine fixative
glutaraldehyde - electron microscopy

24
Q

what are the characteristics of formalin (3)

A
  • is it the universal fixative for anatomical pathology
  • it is used at 10% v/v buffered with saline
  • it is a pungent gas that is soluble in water to 40% by weight
25
Q

how does formalin work

A

it acts by polymerization of protein by forming methylene bridges between adjacent molecules
(formalin attaches to proteins then reacts to produce water and a -CH2- link between the proteins)

26
Q

what is the fixative of choice for cytology smears

A

Ethanol and Methanol

27
Q

how does ethanol / methanol fixation work

A

disruption of hydrophobic bonds and replacement of water with the ethanol

28
Q

what are 2 facts about ethanol / methanol fixation

A
  • it has a rapid effect with pronounced shrinkage
  • it does not affect the reactive antigen sites
29
Q

what are 3 physical agents used for fixation

A
  1. microwave
  2. heat
  3. untrasound
30
Q

what are the advantages and disadvantages of using microwave as fixation

A

advantages:
- rapid (heat acceleration)
- no change in volume of tissue
- facilitates the staining reaction
- preservation of tissue

disadvantages:
- may produce a toxic gas ( due to immersion in NBF)
- has a risk of heat injury

31
Q

when is heat fixation used

A

for microorganisms

32
Q

what are the 4 principles (steps) of tissue processing

A

1.dehydration (in ethanol) to remove water
2. clearing (in xylene) remove dehydration agent
3. impregnation - replace clearing agent
4. embedding (in paraffin wax)

33
Q

what is the overall process of a routine histopathology

A
  • specimen provided by surgical procedure
  • preserve tissue (fixation)
  • process tissue - (dehydration, clearing, impregnation, embedding)
  • Microtomy
  • staining
  • microscopy
  • report
34
Q

what are the 2 section margins when looking at a sample

A
  • En Faced margins
  • Perpendicular margins
35
Q

describe the 2 types of automated tissue processors

A

Fluid transfer - sample is still and different fluids are pumped around it in a specific order (≈300 cassette capacity)
Tissue transfer - samples are moved into different reservoirs according to a cycle (≈ 100 cassette capacity)

36
Q

what is the standard procedure for tissue processing

A

1 hour in each ethanol station
1 hour in each xylene station (3of)
1 hour in each of the wax baths under vacuum
embed in wax

37
Q

what slice thickness for a sample is needed for a Light microscope and a transmission electron microscope

A

LM = 1-10um
TEM = 10um
the machine can cut a range of 0.5um to 50um

38
Q

what is the staining mechanism of H+E

A

Eosin ions are anionic and stains cations (anything that is stained is call acidophilic) eg proteins

cationic Methylene blue ions stain tissue anions (stains basophilic) eg nucleus

39
Q

what 2 types of investigations are done in diagnostic pathology

A
  • screening investigation: Normal population or population at risk
  • diagnostic investigation: symptomatic patients
40
Q

what are the 3 ways of collecting a sample in pathology

A
  • exfoliative-passively shed epithelial cells
  • abrasive- manually taken epithelial cells
  • fine needle aspiration

MEDI (11 decks)

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