Tissue sections are thin slices of biological tissue used in microscopy for diagnostic, research, and educational purposes. This guide explores the techniques of tissue sectioning, staining, and analysis, highlighting their importance in histology and pathology.
Table of Contents
Introduction to Tissue Sections
Tissue Preparation for Sectioning
Fixation
Dehydration
Clearing
Embedding
Microtomy: Cutting Tissue Sections
Types of Microtomes
Section Thickness
Staining Techniques for Tissue Sections
Hematoxylin and Eosin (H&E)
Special Stains
Immunohistochemistry (IHC)
Applications of Tissue Sections
Medical Diagnostics
Research and Drug Development
Education
Challenges and Troubleshooting in Tissue Sectioning
Future Trends in Tissue Section Technology
Conclusion
1. Introduction to Tissue Sections
Tissue sections are fundamental in histology, enabling scientists and pathologists to study cellular structures under a microscope. These thin slices, typically 4–10 micrometers thick, are prepared using specialized techniques to preserve tissue architecture.
Tissue sections are crucial in:
Diagnosing diseases (e.g., cancer, infections)
Studying tissue morphology
Conducting biomedical research
The process involves tissue fixation, embedding, sectioning, and staining to enhance visibility.
2. Tissue Preparation for Sectioning
Fixation
Fixation preserves tissue structure by preventing decomposition. Common fixatives include:
Formalin (10% buffered formalin) – Most widely used
Ethanol & Methanol – For cytological preparations
Glutaraldehyde – For electron microscopy
Dehydration
Water is removed using graded alcohols (70% to 100%) to prepare tissues for embedding.
Clearing
Alcohol is replaced with xylene or toluene, making tissues transparent and ready for wax infiltration.
Embedding
Tissues are embedded in paraffin wax or resin to provide support for thin sectioning.
3. Microtomy: Cutting Tissue Sections
Types of Microtomes
Rotary Microtome – Most common for paraffin sections
Cryostat – For frozen sections
Vibrating Microtome – For soft tissues (e.g., brain)
Ultramicrotome – For electron microscopy (nanometer-thin sections)
Section Thickness
Routine histology: 4–10 µm
Frozen sections: 5–15 µm
Electron microscopy: 50–100 nm
Thin sections are floated on a water bath to remove wrinkles before mounting on slides.
4. Staining Techniques for Tissue Sections
Hematoxylin and Eosin (H&E)
Hematoxylin stains nuclei (blue/purple)
Eosin stains cytoplasm and extracellular matrix (pink)
Special Stains
Periodic Acid-Schiff (PAS) – Detects carbohydrates (e.g., glycogen)
Masson’s Trichrome – Highlights collagen (blue) and muscle (red)
Oil Red O – Stains lipids in frozen sections
Immunohistochemistry (IHC)
Uses antibodies to detect specific proteins (e.g., HER2 in breast cancer).
5. Applications of Tissue Sections
Medical Diagnostics
Cancer detection (biopsy analysis)
Infectious disease identification (e.g., tuberculosis in lung tissue)
Research and Drug Development
Studying disease mechanisms
Testing drug effects on tissues
Education
Teaching anatomy and pathology
6. Challenges and Troubleshooting in Tissue Sectioning
Folding or tearing – Due to improper microtome handling
Poor staining – Inadequate fixation or dehydration
Artifacts – Bubbles, knife marks
Solutions:
Use sharp blades
Optimize fixation time
Adjust microtome settings
7. Future Trends in Tissue Section Technology
Digital Pathology – AI-assisted diagnosis
3D Histology – Reconstructing tissue volumes
Automated Staining Systems – Improving consistency