What is Sectioning?
Sectioning is a crucial step in histology that involves cutting tissue samples into very thin slices to be examined under a microscope. This process allows researchers and pathologists to study the microanatomy of tissues, cells, and organs in great detail.
Why is Sectioning Important?
Sectioning is essential because it enables the visualization of the internal structure of tissues. Without thin sections, it would be impossible to observe the intricate details that are crucial for understanding normal tissue architecture and identifying pathological changes.
What Tools are Used for Sectioning?
The primary tool used for sectioning is the
microtome. A microtome is a sophisticated instrument designed to cut extremely thin sections of tissue. Different types of microtomes, such as rotary, cryo, and ultramicrotomes, are used depending on the specific requirements of the tissue and the study.
Fixation: The tissue sample is preserved using fixatives like formaldehyde to prevent degradation.
Embedding: The fixed tissue is embedded in a solid medium, usually paraffin wax, to provide support for thin sectioning.
Trimming: Excess embedding medium is trimmed away, leaving a small block that contains the tissue.
Sectioning: The block is mounted on the microtome, and thin slices are cut. These sections are typically 3-5 micrometers thick for light microscopy and even thinner for electron microscopy.
Mounting: The thin sections are then placed on glass slides.
Staining: Sections are stained using various dyes to enhance contrast and highlight specific structures.
Types of Microtomes
There are several types of microtomes used in histology: Rotary Microtome: Commonly used for routine paraffin-embedded tissue sectioning.
Cryostat Microtome: Used for cutting frozen tissue sections, often in situations where rapid diagnosis is required.
Ultramicrotome: Used for cutting extremely thin sections for electron microscopy.
Thickness Variability: Maintaining uniform thickness across sections is critical for accurate analysis.
Tissue Artifacts: Poor technique can introduce artifacts such as folds, tears, or chatter marks in the sections.
Embedding Medium: Proper embedding is crucial; incorrect embedding can make sectioning difficult.
Training: Technicians and pathologists are trained extensively to master sectioning techniques.
Equipment Maintenance: Regular maintenance of the microtome and other equipment ensures consistent performance.
Section Examination: Each section is examined for defects before staining and mounting.
Staining and its Importance
Staining is an essential part of the sectioning process. It involves applying various dyes to the tissue sections to enhance contrast and reveal specific structures. Common stains include
Hematoxylin and Eosin (H&E), which are used to differentiate between different tissue components.
Applications of Sectioning
Sectioning has numerous applications in medical and research fields, including: Pathology: Diagnosing diseases by examining tissue samples.
Histopathology: Studying the microscopic structure of diseased tissues.
Research: Understanding the basic biology of tissues and organs.
Conclusion
Sectioning is an indispensable technique in histology that enables detailed examination of tissue architecture. Through careful preparation, cutting, and staining, sectioning provides valuable insights into both normal and pathological states, making it a cornerstone in medical diagnostics and biological research.
