Histology: Specimen to Slide Flashcards
What do you put a histology sample in at collection?
10% neutral buffered formalin
Why is it important to put tissue is a fixative after it’s collected?
Prevents autolysis and other changes, helps with staining and allows for better contrast between tissues.
What is the minimum ratio for formalin to tissue?
10:1
At what rate does formalin fix tissues?
~1mm/hour
What is the minimum time required for fixation in 10% NBF?
At least 24 hours.
What other fixatives can you use to harden autolysed and neural tissues?
Bouin’s or Davidson’s
What tissues can you use Bouin’s or Davidson’s to fix?
Autolysed tissues, neural tissue, eyes, fetal tissue, and uterine biopsies.
What should you do if the sample is really bloody or contaminated with lots of organic material?
Change the formalin after 24 hours.
If the tissues is very large, what should be done to help ensure fixation throughout?
Breadloaf or cut the tissues into slices no thicker than 1 cm to let the fixative penetrate more effectively.
What should you include in a tissue sample?
Both the lesion and normal tissue.
What should you include in a sample of tissue without an obvious lesion?
All tissue layers.
What should the surgeon do with masses requiring a margin assessment?
Mark the orientation with something like suture.
What should the histology technician do with masses that require a margin assessment before trimming do?
Ink the mass.
What is the ideal thickness of a tissue?
3mm
What special step is required with bone samples?
Bone must fix for 24 hours and then be exposed to a decalcifier until it’s demineralized (can take up to a week).
What special step is required with keratinized samples (eg. hoof or nail)?
Must be softened.
What is the basic concept of processing?
To replace the tissue’s water with wax.
What is the purpose of the graded alcohols during processing?
Alcohol replaces the water to prepare the sample for the next step.
What is used during processing after the graded alcohol treatment?
Xylene, which replaces the alcohol in preparation for the next step.
What is uses during processing after the Xylene treatment?
Parafin, which replaces the Xylene.
What is the purpose of a processor?
It exposes the tissues to each solution (alcohol, Xylene, parafin) for the appropriate amount of time.
What aids the processor in its process?
Vacuum and pressure which help the solution penetrate the tissue.
What is embedding?
Creates a tissue block by adding paraffin around the treated tissue sample.
What is a microtome?
Used to cut the paraffin embedded tissues.
