CONVENTIONAL TISSUE PROCESSING Flashcards
In order to enable the pathologist to diagnose the presence or absence of disease, the histotechnologist needs to produce a [?] of good quality that allows for adequate interpretation of microscopic cellular changes.
tissue section
Solid tissues need to be fixed and processed to preserve their structures, and eventually impregnated with an appropriate hardening substance to permit making thin slices suitable for staining and microscopic evaluation. This can be accomplished by preserving and carefully processing solid structures and tissues in the following order:
- Fixation
- Decalcification (optional)
- Dehydration
- Clearing
- Impregnation (Infiltration)
- Embedding
- Trimming
- Section-Cutting (Microtomy)
- Staining
- Mounting
- Labeling
describes the various steps required to take the tissue from fixation to the state where it is completely infiltrated with a suitable histological wax and can be embedded ready for section cutting on the microtome.
“Tissue processing”
Once the tissue has been fixed, it must be processed into a form in which it can be made into
thin microscopic sections.
[?] cannot be directly infiltrated with paraffin. First, the water from the tissues must be removed by dehydration. This is usually done with increasing concentrations of alcohol (?).
Wet fixed tissues (in aqueous solutions)
70% to 95% to 100%
Because [?] are not miscible, the specimens must be gradually dehydrated to achieve complete replacement of water with alcohol.
water and paraffin
Once successfully dehydrated, the next step is called “?” and consists of removing the dehydrating agent (alcohol) with a substance that will be miscible with the embedding medium (paraffin).
clearing
The commonest clearing agent is
xylene.
Finally, the tissues are infiltrated with an embedding agent (almost always [?]).
paraffin
dehydrating agent (?)
alcohol
embedding medium (?)
paraffin
