Histology laboratory equipment

Table of contents

Introduction

Histology laboratory equipment is essential for preparing and examining tissue samples for microscopic study.
These tools ensure proper fixation, processing, sectioning, and staining of tissues.
Microtomes and cryostats enable the cutting of thin, accurate tissue sections.
Tissue processors automate dehydration, clearing, and infiltration steps for uniform results.
Embedding centers and water baths support proper block orientation and section handling.
Staining equipment enhances tissue contrast for clear visualization under the microscope.
Microscopes are crucial for analyzing cellular details and identifying pathological features.
Fume hoods provide a safe workspace for handling hazardous chemicals used in histology.
Refrigerators, pH meters, and storage systems help maintain reagent quality and stability.
Proper maintenance of all equipment ensures consistent, accurate, and safe laboratory performance.

Laboratory Equipment

Microtome

Principle

A microtome advances a paraffin-embedded tissue block toward a sharp steel/ceramic blade at controlled thickness increments (1–20 µm), producing reproducible thin sections.

Uses

Cutting thin sections (typically 3–5 µm for routine H&E; 7–10 µm for special stains like Congo Red).
Essential for creating high-quality tissue ribbons without compression, chatter, or tearing.
Used for paraffin, resin, and cell blocks.

Maintenance Practices

1. Blade Care

Replace disposable blades once they show dullness (compression artifacts, chatter).
Handle blades with forceps; never with fingers.
Store unused blades in a dry environment to prevent rusting.

2. Cleaning

Clean microtome stage, clamps, and knife holder daily with xylene-free or non-corrosive disinfectant.
Remove wax residues with mild heat or xylene (according to lab SOP).

3. Lubrication & Mechanical Checks

Lubricate moving parts weekly (using manufacturer-recommended oils).
Check block holder alignment to avoid tilted sections.

4. Calibration

Verify thickness settings monthly with calibration blocks or plastic strips.
Confirm even advancement of handwheel.

Best Practices

Always lock the microtome when not in use.
Maintain room at 18–22°C and moderate humidity for optimal sectioning.
Avoid excessive force during block trimming.

Cryostat

Principle

A cryostat is a refrigerated chamber containing a microtome for cutting frozen tissue sections at −20°C to −30°C, preserving lipids, enzymes, and antigens.

Uses

Intraoperative rapid diagnosis (frozen sections).
Immunofluorescence (renal biopsies).
Lipid staining (Oil Red O), as lipids dissolve in paraffin.
Enzyme histochemistry requiring rapid freezing.

Maintenance Practices

1. Temperature Checks

Verify chamber temperature daily.
Maintain:
- −20°C for soft tissues
- −30°C for dense tissues like muscle

2. Blade Maintenance

Replace blades frequently due to rapid dulling from cold cutting.
Dispose of blades in puncture-proof sharps container.

3. Cleaning & Disinfection

Remove tissue debris after each use.
Perform weekly defrost cycles to remove frost buildup.
Use 70% ethanol or cryostat-safe disinfectants.
UV disinfection (if present) should be run at least once per day.

Best Practices

Keep chamber closed as much as possible to prevent ice accumulation.
Wear PPE—cryostat can aerosolize tissue particles.
Maintain separate cryostat for infectious specimens.

Tissue Processor (Automatic / Semi-automatic)

Principle

Automated movement of tissues through dehydration (alcohols), clearing (xylene/ substitutes), and paraffin infiltration.

Uses

Provides uniform processing for consistent tissue morphology.
Saves labor and reduces human error in multiple reagent transfers.
Ensures optimal infiltration for easy microtomy.

Maintenance Practices

1. Reagent Management

Monitor alcohol/xylene/paraffin levels daily.
Replace reagents based on cycles, color change, or impurity load.
Maintain logs for reagent changes for QA audits.

2. Chamber Cleaning

Clean retort with warm paraffin or alcohol-based cleaning solutions.
Check tubing for blockages or leaks weekly.

3. Calibration

Validate timing, pressure cycles, and temperature monthly.
Ensure paraffin bath remains at 2–4°C above melting point.

Best Practices

Use standardized cassette loading patterns to ensure even infiltration.
Avoid overloading retort—causes incomplete processing.
Monitor tissue size recommendations (usually <4–5 mm thickness).

Embedding Center (Embedding Station)

Principle

Maintains molten paraffin for embedding tissues into blocks, enabling correct orientation for sectioning.

Uses

Embedding tissues in paraffin with correct anatomical orientation.
Solidifying blocks on a cold plate for microtomy.

Maintenance Practices

1. Temperature Control

Paraffin reservoir: 58–60°C
Heated forceps wells: slightly above melting point
Cold plate: −5°C to −10°C

2. Cleaning

Remove paraffin spills immediately.
Weekly cleaning of dispensing nozzles to prevent clogging.

3. Paraffin Quality

Replace paraffin when discolored or contaminated.

Best Practices

Pre-warm cassette and mold to prevent bubbles.
Ensure tissue is fully surrounded by paraffin (no air pockets).

Staining Equipment (Manual Racks / Automatic Stainers)

Principle

Sequential application of dyes, buffers, differentiators, and bluing agents to produce contrast.

Uses

H&E staining (routine).
Special stains (PAS, Masson’s Trichrome, reticulin, silver).
Ensures reproducible staining for diagnostic quality.

Maintenance Practices

1. Daily Cleaning

Wash racks post-use with mild detergent.
Remove precipitates and dye residues.

2. Reagent Monitoring

Replace hematoxylin when oxidized.
Monitor alcohol and xylene purity.
Check expiration dates and clarity of solutions.

3. Calibration (Automatic Stainers)

Validate dip times, agitation patterns, and temperature settings.
Check robotic arms and slide holders.

Best Practices

Maintain consistent staining protocols across all staff.
Use control slides daily to detect staining variability.

Microscope (Brightfield Microscope)

Principle

Uses transmitted light and optical magnification (4×–100× objectives) to visualize stained tissue architecture.

Uses

Routine examination of H&E-stained slides.
Identifying morphology, cell details, and pathological lesions.
Higher-end microscopes allow phase-contrast and fluorescence.

Maintenance Practices

1. Optics Care

Clean lenses only with lens paper + certified lens cleaning solution.
Never use alcohol on objectives with special coatings.

2. Light Source

Replace halogen/LED bulbs when dim.
Keep condenser clean and correctly aligned.

3. Calibration

Check mechanical stage movement and focus accuracy quarterly.

Best Practices

Use dust covers when not in use.
Store objectives in dry, controlled environments.
Avoid touching optical components.

Water Bath (Floatation Bath)

Principle

Heated water spreads paraffin ribbons, helping remove wrinkles before slide mounting.

Uses

Flattening paraffin sections (40–45°C).
Essential for high-quality section mounting.

Maintenance Practices

1. Water Quality

Change water daily.
Add thymol to prevent fungal growth.

2. Temperature Monitoring

Maintain 8–10°C below paraffin melting point.
Use external thermometer—built-in thermostats may drift.

3. Cleaning

Remove wax debris with lint-free wipes.
Weekly deep cleaning with mild detergents.

Best Practices

Avoid overheating water—causes tissue overexpansion.
Do not overload bath at once.

Fume Hood

Principle

Removes hazardous vapors (xylene, formalin, ammonia) via continuous airflow.

Uses

Tissue grossing
Staining procedures
Handling volatile solvents

Maintenance Practices

1. Airflow Checks

Measure face velocity monthly (target: 100–120 ft/min).
Check alarm systems (if present).

2. Cleaning

Wipe interior surfaces daily.
Remove spills immediately.

3. Filter Replacement

Replace charcoal or HEPA filters per manufacturer’s schedule (usually 6–12 months).

Best Practices

Keep sash at recommended height.
Never store chemicals permanently inside hood.
Ensure uninterrupted airflow (no blocking grids).

Refrigerator / Freezer

Uses

Storage of antibodies, dyes, control tissues, and samples.
Prevents degradation of temperature-sensitive reagents.

Maintenance Practices

1. Temperature Monitoring

Record daily readings (2–8°C for refrigerators, −20°C/−80°C for freezers).
Maintain temperature logs for audits.

2. Organization & Cleaning

Remove expired chemicals weekly.
Prevent overcrowding for optimal air circulation.

3. Labeling

All items must have:
- Name
- Date of preparation
- Expiry
- Responsible technician

Best Practices

Use dedicated units for biologics vs chemicals.
Attach backup power or alarm systems for critical storage.

pH Meter

Principle

Uses glass electrode potential changes to measure hydrogen ion concentration.

Uses

pH adjustment of hematoxylin.
Buffer preparation for special stains.
Ensures consistency in staining outcomes.

Maintenance Practices

1. Calibration

Calibrate with standard buffers (pH 4, 7, 10) before each use.

2. Electrode Care

Rinse electrode with distilled water between readings.
Store electrode in manufacturer-recommended solution—never dry.

3. Routine Checks

Inspect electrode for cracks or air bubbles.

Best Practices

Replace electrodes annually.
Do not use contaminated buffers.

General Best Practices for Histology Labs

1. Staff Training & Competency

Regular training sessions for microtomy, staining, and safety.
Competency assessments every 6–12 months.

2. Standard Operating Procedures (SOPs)

Document all equipment use, cleaning, QC, and troubleshooting.
Keep updated SOPs accessible in the lab.

3. Quality Control (QC)

Use daily control slides for H&E and special stains.
Monthly instrument calibration & validation logs.
Participate in external quality assurance (EQA) programs.

4. Inventory Management

Maintain stock registers.
Track expiry dates.
Avoid reagent shortages.

5. Waste Management

Dispose of xylene, formalin, and solvents per biomedical waste rules.
Use color-coded containers for sharps, tissues, chemicals.

6. Emergency Preparedness

Fire extinguishers, spill kits, eyewash stations readily available.
SOPs for equipment failure, power outage, or chemical spills.

MCQs

1. Which instrument is used to cut very thin sections of paraffin-embedded tissue?

A. Cryostat
B. Microtome
C. Tissue processor
D. Embedding center

2. The cryostat typically operates at which temperature range?

A. 0 to 5°C
B. −5 to −10°C
C. −20 to −30°C
D. −40 to −60°C

3. The main purpose of a tissue processor is to:

A. Stain tissues
B. Dehydrate, clear, and infiltrate tissue
C. Freeze tissues
D. Embed tissues in wax

4. Which equipment is used to embed tissues in paraffin?

A. Microtome
B. Embedding center
C. Water bath
D. Fume hood

5. A water bath in histology is mainly used to:

A. Cut thin sections
B. Freeze tissues
C. Float tissue sections
D. Dry slides

6. The microscope most commonly used in routine histology is:

A. Electron microscope
B. Fluorescence microscope
C. Inverted microscope
D. Brightfield microscope

7. Which reagent-sensitive equipment requires frequent pH calibration?

A. Water bath
B. pH meter
C. Microtome
D. Cryostat

8. The fume hood is mainly used to:

A. Sharpen blades
B. Prevent chemical exposure
C. Clean slides
D. Incubate reagents

9. Cryostat sections are commonly used for:

A. H&E routine staining
B. Immunofluorescence
C. Heavy metal stains
D. Electron microscopy

10. Which equipment helps flatten paraffin sections?

A. Tissue processor
B. Microtome
C. Water bath
D. Coverslipper

11. The main function of the coverslipper is to:

A. Stain tissues
B. Apply permanent mounting medium
C. Dehydrate tissues
D. Store slides

12. Which equipment is used to maintain reagent temperature during embedding?

A. Water bath
B. Embedding center
C. Cryostat
D. Incubator

13. Which of the following removes xylene fumes?

A. Water bath
B. Incubator
C. Fume hood
D. Cryostat

14. A microtome blade becomes dull when:

A. Wax becomes too soft
B. Sections show compression lines
C. Water bath overheats
D. Labels fall off

15. Tissue dehydration mainly occurs in:

A. Water bath
B. Tissue processor
C. Stainer
D. Embedding station

16. A microscope objective with 100× magnification is usually:

A. Dry
B. Immersion oil
C. Fluorescent
D. Polarized

17. The purpose of a cold plate in an embedding center is to:

A. Melt paraffin
B. Rapidly cool paraffin blocks
C. Stain tissues
D. Calibrate microtomes

18. Blade angle adjustment is important for:

A. Staining
B. Embedding
C. Section cutting
D. Slide drying

19. Xylene and formalin must always be handled inside a:

A. Water bath
B. Incubator
C. Fume hood
D. Cryostat

20. Which equipment checks the acidity or alkalinity of staining solutions?

A. Refractometer
B. pH meter
C. Spectrophotometer
D. Microscope

21. The paraffin melting point in embedding centers is typically:

A. 20–30°C
B. 35–40°C
C. 55–60°C
D. 90–100°C

22. For proper cryostat sectioning, tissues must be:

A. Dehydrated
B. Frozen
C. Cleared
D. Embedded

23. Which equipment uses UV or HEPA filters?

A. Microtome
B. Fume hood
C. Tissue processor
D. Water bath

24. A common cause of wrinkled sections is:

A. Overheated water bath
B. Cold paraffin
C. Sharp blade
D. Newly cleaned microtome

25. Embedding molds are used in:

A. Processing
B. Staining
C. Microtomy
D. Embedding

26. Automation of H&E staining is done using:

A. Coverslipper
B. Automatic stainer
C. Microtome
D. Incubator

27. Reagents like hematoxylin should be stored in:

A. Dark bottles
B. Sunlight
C. Freezers
D. Open containers

28. The equipment that prevents operator exposure to toxic vapors is:

A. Microtome room
B. Fume hood
C. Water bath
D. Microscope

29. Inadequate dehydration in a tissue processor leads to:

A. Floatation artifacts
B. Poor paraffin infiltration
C. Thick sections
D. Overstaining

30. Which piece of equipment stabilizes tissue blocks before cutting?

A. Cold plate
B. Water bath
C. Stainer
D. pH meter

31. The main reason for using a refrigerator in histology is:

A. Freeze tissues
B. Store reagents and stains
C. Dehydrate tissues
D. Grow bacteria

32. Lens cleaning should be done using:

A. Cotton cloth
B. Tissue paper
C. Lens paper
D. Gauze

33. Calibration of microtome ensures:

A. Correct section thickness
B. Correct stain color
C. Correct reagent pH
D. Correct slide labeling

34. A tissue that is too hard to section may require:

A. More dehydration
B. Re-embedding
C. Soaking in ice water
D. Heating

35. The main hazard when working with cryostats is:

A. Burns
B. Chemical fumes
C. Aerosolized infectious tissue
D. Radiation

36. The instrument used to mount tissue sections on slides is:

A. Stainer
B. Water bath
C. Microtome
D. Coverslipper

37. Formalin-fixed tissues are processed using:

A. Cryostat
B. Tissue processor
C. Electron microscope
D. pH meter

38. Brightfield microscopy uses which light source?

A. UV
B. Infrared
C. Visible light
D. X-rays

39. A wax dispenser is part of which histology equipment?

A. Cryostat
B. Embedding center
C. Microtome
D. Stainer

40. Which equipment requires daily removal of paraffin debris?

A. Microscope
B. Water bath
C. pH meter
D. Incubator

✅ Answer Key

Introduction

Laboratory Equipment

Microtome

Cryostat

Tissue Processor (Automatic / Semi-automatic)

Embedding Center (Embedding Station)

Staining Equipment (Manual Racks / Automatic Stainers)

Microscope (Brightfield Microscope)

Water Bath (Floatation Bath)

Fume Hood

Refrigerator / Freezer

pH Meter

General Best Practices for Histology Labs

MCQs

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