MLHG 106 - Introduction to Histology and Cytology: Lesson 2 Vocab Flashcards

100 vocabulary flashcards drawn from the lecture notes covering grossing, processing, embedding, microtomy, cryostat and safety concepts.

Grossing

Macroscopic evaluation of a surgical specimen after fixation, including labeling, description, and sampling decisions.

Macroscopic evaluation

Visual inspection of tissue size, shape, color, and surface features used to guide sampling.

Gross specimen

The tissue piece prepared for processing after grossing.

Patient name labeling

The patient’s name printed on the specimen to identify its source.

Assigned number

A unique case number assigned to a tissue specimen for traceability.

Surgical procedure

The operation from which tissue was removed; noted during grossing.

Tissue size

Dimensions of tissue measured with a ruler (in millimeters).

Tissue weight

Mass of tissue measured on a balance or scale.

Tissue colour

Visual description of tissue color observed grossly.

Tissue consistency

Texture of tissue (soft, firm, friable) observed during grossing.

Ink margins

India ink or silver nitrate used to mark margins or lesions on tissue.

No section taken

Notation when tissue cannot be processed; specimen is accessioned, described, and stored.

Tissue cassette

Plastic container with perforations to allow reagents to immerse tissue.

Perforations

Small holes in a cassette that enable reagent penetration during processing.

Tight fitting lid

Lid design that prevents tissue loss during processing.

Color-coding

Color system used to identify cassette contents; not universal across labs.

Yellow cassette

Cassette color code used for neuro tissue.

Green cassette

Cassette color code used for biopsies.

Blue cassette

Cassette color code used for autopsies.

White cassette

Cassette color code used for other tissues (e.g., lung).

Automatic cassette labelling

Printer-based labeling system interfaced with the LIS for cassette identification.

LIS (Laboratory Information System)

Digital system used to track specimens and processing steps.

Accurate numbering

Precise, consistent numbering throughout processing to prevent diagnostic errors.

Incorrect or missed diagnosis

Potential consequence of labeling or processing errors.

Grossing station

Workstation setup for grossing, including board, blades, and tools.

Dissecting board

Flat surface used to place tissue for grossing and dissection.

Scalpel

Sharp knife used for incisions during grossing and sampling.

Forceps

Tweezers used to handle tissue during grossing and processing.

Scissors

Cutting instrument used to trim tissue.

Ruler

Measuring tool for documenting tissue size.

Dissecting knife

Knife used for detailed tissue dissection.

Sieve

Strainer used to wash or rinse tissue pieces.

Surgical gloves

Protective gloves to prevent contamination and exposure.

Processing cassettes

Cassettes used to hold tissue during processing and embedding.

Basket

Container for tissue pieces too large for a cassette; placed in fixative.

Analytical balance

Precise scale used to weigh tissue samples.

Sharps container

Container for disposing of sharp instruments safely.

Fixative

Chemical fixative used to preserve tissue morphology.

Formalin

Buffered formaldehyde solution commonly used as a fixative in histology.

Formalin (bone marrow fixation)

Formalin-based fixative variant used for bone marrow tissues.

Decalcification

Removal of calcium salts from calcified tissues to enable sectioning.

Formic acid

Weak organic acid used as a decalcifying agent (5–25%).

Nitric acid

Strong inorganic acid used for rapid decalcification; may damage tissue.

Hydrochloric acid

Strong inorganic acid used in several decalcifying solutions.

EDTA

Chelating agent that binds calcium; gentle and slow decalcification.

Gooding and Stewart Fluid

Decalcifying solution composed of formic acid, formalin, and water.

Van Ebner’s Fluid

Decalcifying solution containing hydrochloric acid, sodium chloride, and water.

RDO

Commercial decalcifying solution with hydrochloric acid.

Bone thickness

Bone should be cut into 4–5 mm thick slices for processing.

End-point determination (decalcification)

Methods to assess completion: probing pliability, X-ray, or chemical tests.

Probing

Manual assessment of tissue pliability to judge decalcification status.

X-ray end-point

Radiographic check to ensure all calcium has been removed.

Chemical test

Chemical check for calcium in the decalcifying solution.

Tissue processing

Sequential steps to prepare tissue for embedding: dehydration, clearing, and wax infiltration.

Dehydration

Removal of water from tissue using graded alcohols.

Ethanol

Alcohol used for dehydration in graded concentrations.

Absolute ethanol

100% ethanol used in final dehydration steps.

Isopropanol

Alternative dehydrating agent occasionally used; may cause more tissue shrinkage.

Acetone

Alternative dehydrating solvent; rarely used in histology.

Clearing

Replacement of dehydration reagent with a solvent miscible with paraffin; tissue becomes transparent.

Xylene

Common clearing agent; raises tissue refractive index; miscible with paraffin; highly volatile and toxic.

Toluene

Clearing agent alternative to xylene; slower but less aggressive on tissue; volatile.

Chloroform

Clearing agent; effective but toxic and less commonly used.

Cedar wood oil

Natural clearing agent; less toxic option used in some protocols.

Refractive index

Measure of how light propagates through tissue; increased by clearing agents for better microscopy.

Miscibility with alcohol

Clearing agents are not water-miscible; many are not fully miscible with water but replace alcohol in clearing steps.

Paraffin infiltration

Replacement of clearing agent with molten paraffin wax to embed tissue.

Paraffin wax

Inert hydrocarbon wax used to embed tissue; melts around 40–70°C.

Melting point

Temperature range at which paraffin wax melts, typically 40–70°C.

Beeswax

Wax additive that reduces crystal size and improves adhesion and ribbon formation.

Rubber additive

Wax additive that increases elasticity and adhesion of embedded tissue.

Plastics additive

Wax additive to increase hardness and support for embedding.

Paraplast

Paraffin wax blended with plastic polymers to improve elasticity and cutting quality.

Embedding center

Workstation with a hot paraffin area and a cold area for solidification.

Mold

Container used to shape paraffin around tissue during embedding.

Tissue orientation

Positioning tissue in the mold so the long axis aligns with the mold edge.

Long axis alignment

Aligning the tissue’s longest dimension parallel to the mold’s edge for optimal sectioning.

Wax margin

Edge of wax around tissue to help orientation and cutting.

Block face

The surface of the solidified paraffin block containing the embedded tissue.

Ice in embedding

Placing blocks on ice to speed solidification before sectioning.

Embedding temperatures

Critical temperatures for embedding steps (hot plate and molten wax ranges).

Mold too small

Embedding problem where tissue touches mold edges, hindering sectioning.

Tissue floating

Tissue not fully embedded due to incomplete dehydration or fixation; can drift in wax.

Air bubbles

Air pockets within wax that create defects in blocks.

Wax stratification

Layering of wax components causing uneven block quality.

Cross-contamination

Spread of tissue from one block to another during embedding if not careful.

Embedding contamination prevention

Practices to prevent cross-contamination (one cassette at a time, wipe forceps, etc.).

Embedding checklist

Pre-leaving-lab list to verify equipment and supplies (switches, molds, gauze, forceps, pencils, etc.).

Gauze

Woven material used during embedding to hold tissue and prevent loss.

Forceps cleaning

Wiping forceps between specimens to prevent cross-contamination.

Pencils

Lead pencils used to mark cassettes or blocks and note orientation.

Cassettes

Tissue containment units used during processing and embedding.

Labeller

Device used to print and apply labels to cassettes.

Waste receptacle

Container for disposing of contaminated materials and wax waste.

Microtomy

Sectioning of tissue blocks to produce thin slices for mounting on slides.

Rotary microtome

A manual, semi-automatic, or automatic instrument that cuts thin tissue sections.

Knife blade

Very sharp blade required for clean, uniform sections.

Block holder

Clamp that holds the tissue block steady during sectioning.

Ribbon

Continuous series of tissue sections produced by the knife and collected together.

Water bath

40–45°C flotation bath used to flatten ribbons before mounting on slides.