LAB Ex4a Flashcards
the word ‘tissue’ was defined in the late 1700s by the father of histology who is:
Marie Francois Bichat
the gold standard for tissue
fixation
Formaldehyde
Formaldehyde was discovered by:
Butlerov (1859)
Factors affecting the tissues that render them suboptimal for histologic preparation before arriving in the laboratory.
pre-analytical factors
Five pre-analytical factors:
- warm ischemia
- cold ischemia
- fixation
- properly filled surgical pathology requests
- accessioning procedure
term used for the initial anoxic insult a tissue suffers when its blood supply is cut off.
Warm ischemia
The duration of warm ischemia depends on the particular circumstance of the surgery, like:
speed and skill of the surgeon
the lack of oxygen once the tissue sample is removed from the patient’s body and before all metabolic processes are stopped by fixation.
Cold Ischemia
ensures that the tissue can be processed properly for frozen sections, imprints, etc.
circulating nurse immediately transports the fresh tissue to the laboratory
should be sectioned serially
Larger tissues
opened to expose mucosal linings
uteri and intestines
should be quickly immersed in fixative
Small biopsies
Properly preserved tissues are more resistant to
artifacts
the surgical pathology request should be properly-filled up by the:
clinician asking for diagnosis
Surgical Pathology Request should include:
patient’s history
physical and laboratory findings
imaging findings
pre-operative and post-operative diagnosis (if different)
Specimens submitted to the histopathology laboratory must be entered into the surgical pathology database via the:
accessioning process
absolutely unacceptable for accessioning
Unlabeled specimens
Proper identification includes matching the data on the:
specimen container label
surgical pathology request form
If there are inconsistencies between the two, the specimen and request form are returned to the OR for:
correction
five criteria for specimen rejection
> discrepancies between requisition and specimen label > no labels or mislabeled > leaking container > absent clinical data or history > inappropriately identified specimens
Standard dissecting kits/sets which are available locally contain one or more of the following:
> scissors;
forceps;
blade holders
blades.
Cutting tools must always be kept clean before and after use to avoid:
carrying a tissue over
Blades should be disposed off in:
“sharps” containers
The basic features of a gross laboratory include the following:
> sink > stable table top; > water supply; > irrigation system; > fume extraction system/ventilation system ✓ waste disposal unit
The weight of intact specimens is taken and rounded to the nearest:
0.1 g
In this specimen, the gross weight may be more important than the histopathology characteristics in arriving at a diagnosis.
hyperplastic thymic tissue
Dimensions are taken and rounded to the nearest:
1.0 cm
characteristics to report in gross description of specimens
> weight
dimensions
color
consistency
After adequately examining them for completeness and describing their gross features, specimens are:
dissected
Small specimens are sectioned serially, about ____ thick
2 to several mm
why are small specimens sectioned serially?
to look for small lesions
Representative sections are also taken from ____ for comparison
normal structures
For large specimens, the sections are cut into _____
1.0 cm thick sections
Sectioning large specimens to ensure that pathologic areas or tumoral areas are identified is called:
bread loafing
structures that must be opened as part of initial examination
hollow structures
For specimen with tumors, the following must be identified:
✓ site and size of the tumor; ✓ location and structures invaded by the tumor; ✓ vascular invasion; ✓ distance from resection margins; and ✓ presence of lymph nodes
standard tissue cassettes measure:
3.0 x 2.5 x 0.4 cm
Specimens must fit easily into the cassette and should not be more than:
0.3 cm in thickness
the accession number of the specimen should be written in:
pencil
Tissue processing can be done through the following order:
- Fixation (includes reception, grossing & bread loafing)
- Dehydration
- Clearing
- Infiltration (Impregnation)
- Embedding
- Trimming
- Sectioning
- Staining
- Mounting
the most common fixative
10% formalin
important part of fixation in order to stop the metabolic processes that continue to alter the state of the tissue to be examined.
killing
defined as the alteration of tissues by stabilizing protein so that the tissues become resistant to further changes
fixation
defined as the ratio of velocity of light in air to the velocity of light in a liquid or solid medium.
refractive index
increases the contrast between tissue elements, enabling better appreciation of the structure
difference in refractive indices
The three objectives of fixation include:
(1) preserving the tissue
(2) preventing breakdown of cellular elements
(3) to coagulating or precipitating protoplasmic substances
The 3 benefits of fixation are the following:
(1) allows thin sectioning of tissue by hardening
(2) prevents autolysis and inactivates some infectious agents
(3) improves cell avidity for special stains
most widely used fixative in histopathology today
Ten percent formalin
For general use, 10% formalin is usually buffered to a pH of:
7
Formalin is neutrally buffered to:
prevent formation of black acid hematin pigment.
what type of fixative is formalin
non-coagulant
additive fixative
formalin primarily reacts with:
amino acids containing a reactive hydrogen
when formalin reacts with the amino group on the side chain of amino acids, it forms:
methylene bridges that link the protein chains together
Formalin also cross-links by reacting with:
sulfhydryl groups in the amino acid, cysteine
attracts eosin dye resulting in a pinkish color.
amino group
formalin preserves _____, but leads to gradual loss when storage is prolonged
lipids
dissolves lipids, causing it to appear in routine sections as clear spaces
alcohol and xylene
usually trapped in the tissue by the stabilizing and fixing actions of formalin on protein
glycogen
not fixed by formalin
carbohydrates
rate of penetration of formalin has been established at:
3.6 mm in 1 hour and 7.2
mm in 4 hours.
maximum thickness of tissue for optimal fixation has been set at:
3 mm
Cross-linking is complete in:
24 - 48 hours
excessive cross- linking happens if fixed beyond
48 hours
black acid hematin can be removed when treated with:
alcoholic picric acid
alkaline alcohol
effects of incomplete fixation
- separation of tissue components during microtomy
- poor tissue morphology
- smudgy/bubbling nuclei
- appear more eosinophilic
how many tissue slices for dehydration
4-5
dimension of tissie slices per cassette
2 cm squares that are 3 mm thick
what is the accession number
S-22-01
S (surgical specimen)
22 (year)
01 (specimen serial number)
washing of specimen after fixation is done within
15 minutes to 12 hours
washing of specimen is done with water if the fixatives are:
chromate, formalin, osmic acid
washing of specimen is done with water if the fixatives are:
chromate, formalin, osmic acid
picric acid fixative is washed out with:
50-70% alcohol
mercuric fixative is washed out with
alcoholic iodide
process of removing water using ascending concentration of alcohol
dehydration
procedure of dehydration
70% alcohol for 6 hours, agitate every 24 mins
95% alcohol for 12 hours, agitate every 48 mins
100% alcohol for 2 hours, every 8 mins
100% alcohol for 1 hr, every 4 mins
100% alcohol for 1 hr, every 4 mins
effect of excessive dehydration
hard
brittle
shrunken
effect of incomplete dehydration
soft
not receptive to paraffin
solvent for dehydration
ethanol
solvent for dehydration
ethanol
solvent for clearing
xylene
why is it called clearing agent
impart optical clarity due to high refractive index
process of clearing
two changes of xylene, 1 hour each, agitate every 4 minutes
effect of prolonged clearing
brittle
effect of incomplete clearing
uneven H&E staining
poor nuclear chromatin patterns
paraffin wax is infiltrated into tissue at this temperature
55-60
paraffin wax is solidifed at this temperature
20
