MLHG 106 - Introduction to Histology and Cytology: Lesson 3 Vocab Flashcards

100 vocabulary flashcards covering staining principles, reagents, procedures, safety, and Romanowsky stains from the notes.

Hematoxylin

Natural basic dye from logwood used to stain cell nuclei blue; oxidized to hematein and used with a mordant.

Eosin

Acidic counterstain that stains cytoplasm pink in H&E; pH is controlled for consistent staining.

H&E stain

Hematoxylin and Eosin combination; the routine histology stain for nuclei (blue) and cytoplasm (pink).

Regressive staining

Overstaining with hematoxylin followed by selective decolorization with acid alcohol to control intensity.

Progressive staining

Staining method where tissue is left in hematoxylin until the desired intensity is reached without over-staining.

Acid alcohol

1% hydrochloric acid in 70% ethanol; used to differentiate by removing excess hematoxylin.

Differentiation (staining)

Process of removing excess dye to achieve the target color balance during staining.

Bluing

Alkaline treatment to convert nuclear color to blue; typical pH 8.0–8.5; examples include Scott’s substitute.

Scott’s Tap Water Substitute

Bluing solution used to blue nuclei in H&E; prepared from bicarbonate, magnesium sulfate, and water.

Harris Hematoxylin

Common hematoxylin formulation blended with a mordant for tissue staining.

Mayer’s Hematoxylin

Alternative hematoxylin variant used in histology staining.

Hematoxylin ripening

Oxidation of hematoxylin to hematein, making the dye active for tissue binding.

Mercuric oxide

Oxidizer used in alum hematoxylin preparations to aid ripening and stability.

Potassium alum

Mordant used with hematoxylin to fix the dye to tissue.

Mordant

Substance (e.g., alum) that forms a complex with dye to enhance tissue binding.

Alum hematoxylin preparation

Hematoxylin solution prepared with alum, water, absolute alcohol and mercuric oxide.

Absolute alcohol

100% ethanol used in dehydration and dye preparation.

Distilled water

Pure water used as solvent in reagent preparation.

Deparaffinization

Wax removal from paraffin sections, typically with xylene, prior to hydration.

Hydration

Rehydration of tissue through decreasing alcohol concentrations to water.

95% ethanol

Alcohol step in dehydration/hydration sequence.

70% ethanol

Alcohol step in dehydration/hydration sequence.

Clearing

Treatment with xylene to make tissue transparent prior to mounting.

Cover slipping

Placing a coverslip with mounting medium to protect tissue for microscopy.

Mounting media

Medium (aqueous or resinous) used to mount coverslips; refractive index important.

Permount

Common synthetic resin mounting medium.

DPX

Alternative resinous mounting medium used for permanent slides.

Air bubbles

Trapped air under a coverslip that obscures microscopic detail.

Coverslip thickness

Ideal around 1.5 (about 180 microns); standard coverslips around 150 microns.

Labeling slides

Labels should match slide records and must not overlap the coverslip.

Institute for Quality Management in Healthcare (IQMH)

Organization providing standards for histology storage; long-term retention often 20 years.

Tissue filling

Filling slides/blocks and storing according to IQMH standards (often long-term).

Tissue processing

Sequence: fixation, dehydration, clearing, infiltration, embedding.

Fixation

Preservation of tissue by immersion in fixatives (e.g., formalin) to prevent decay.

Formalin

10% formalin widely used as a fixative in histology.

Zenker’s fluid

Fixative used in some histology protocols.

Bouin’s fluid

Alternative fixative used in histology.

Microtome

Instrument used to cut thin tissue sections for slides.

Sectioning

Cutting tissue into thin sections with a microtome.

Embedding

Infiltration of tissue with paraffin wax to provide support for sectioning.

Dehydration

Removal of water from tissue via ascending ethanol concentrations.

Infiltration

Introduction of embedding medium (paraffin) into tissue.

Paraffin wax

Embedding medium used to support tissue for sectioning.

Staining control slide

Slide known to contain target structures used to verify staining quality.

Control slide

Slide used to verify staining performance.

H&E control slide

Control slide stained with H&E to ensure staining quality.

Staining time accuracy

Precise timing for each staining step; inaccuracies increase variability.

Complete dewaxing

Ensuring all wax is removed before hydration to avoid patchy staining.

PAS stain

Periodic acid–Schiff stain; detects glycogen and lipofuscin; positive for some substances.

Lipofuscin

Pigment that is PAS-positive and accumulates in cells.

Glycogen

Polysaccharide; PAS-positive when present in tissues.

Bile pigments

Pigments that may be PAS-negative in specific contexts.

Hemosiderin

Iron-containing pigment; detected with Perl’s Prussian blue method.

Perl’s method

Prussian blue iron stain used to demonstrate hemosiderin.

Silver impregnation

Stains that deposit silver on certain tissue components (e.g., reticulin).

Reticulin

Fine network of collagen fibers highlighted by silver impregnation.

Gordon & Sweets method

Silver-based method for reticulin staining, notably in kidney tissue.

Positive control

A slide known to contain the target structure used to verify staining works.

Standardize washing

Consistent washing steps to minimize variation in staining outcomes.

Documentation of changes

Record any departures from the established staining protocol.

Microscope setup during differentiation

Careful microscope alignment during differentiation steps to avoid artifacts.

Wet section viewing

Observing sections without coverslips; can affect perceived background depending on condenser setting.

Romanowsky stain

Family of stains for hematology/cytology based on oxidized methylene blue and eosin Y.

Methylene blue

Basic dye in Romanowsky stains; stains acidic components blue.

Azure

Oxidized methylene blue component; contributes to metachromatic hues.

Eosin Y

Pink/red counterstain in Romanowsky stains.

Metachromasia

Romanowsky effect; staining produces multiple hues enabling differentiation of components.

Giemsa stain

Romanowsky-type stain used for malaria and differential white blood cell counts.

Wright stain

Original Romanowsky stain by James Wright; heated methylene blue with eosin Y; may be used with Giemsa.

May-Grünwald-Giemsa stain

Two-step Romanowsky stain (May-Grünwald then Giemsa) giving a broad hue range.

May-Grünwald stain

First step in May-Grünwald-Giemsa; contributes to final metachromatic result.

Leishman stain

Romanowsky variant developed by Leishman; methanol fixation; rapid staining.

Blood film

Peripheral blood smear stained with Romanowsky stains to differentiate cells.

Malaria detection

Use of Romanowsky stains to identify malaria parasites in blood films.

Parasites

Microorganisms detectable by Romanowsky-type stains (e.g., malaria, trypanosomes).

Dewaxing artifacts

Patchy staining caused by incomplete wax removal.

Xylene fumes safety

Work in a fume hood; avoid inhaling fumes from xylene.

Fume hood

Ventilated enclosure used for chemical work to protect from fumes.

Personal Protective Equipment (PPE)

Gloves, lab coat, goggles; essential for handling hazardous reagents.

Automated stainer

Robotized system that standardizes staining and increases throughput.

Manual staining

Hand-staining methods; greater variation and time required.

Quality control in automated staining

Routine use of control slides and verification when reagents or programs change.

Stainer maintenance

Annual preventative maintenance for automated staining systems.

Filter reagents daily

Daily filtration of staining solutions to remove precipitates.

Staining reagents storage

Proper storage conditions (refrigeration, light protection) depending on reagent.

Long-term reagent storage

Some reagents must be refreshed regularly to maintain quality.

Xylol

Alternate term for xylene; used in dewaxing and clearing.

Mounting media refractive index

Mounting media chosen to match tissue optics; resinous media around 1.51–1.55.

Air bubbles under coverslip

Avoid bubbles to prevent obscuring tissue details.

Coverslip labeling

Label should be on the slide and not overlap the coverslip.

Reticulin staining artifacts

Silver impregnation can yield variable reticulin visualization if protocol not followed.

Tissue processing flow order

Fixation → dehydration → clearing → infiltration → embedding.

Tissue cassette labeling

Cassettes are labeled with surgical numbers for traceability.

Staining color in H&E

Nuclei blue and basophilic structures; cytoplasm, collagen, and muscle vary pink shades.

Section thickness

Typical microscopic sections are cut around 5–10 μm depending on method.

IQMH storage standard

IQMH recommends long-term storage of slides/blocks (often 20 years).

Slide storage

Long-term storage of slides and blocks in archival conditions.

Washing steps

Washing steps should be standardized to prevent variability.

Coverslip preparation pitfalls

Avoid partial drying and ensure correct mounting medium to prevent crystal formation.