What is Tissue Handling in Histology?
Tissue handling refers to the meticulous process of collecting, preserving, and preparing tissues for microscopic examination. Proper handling is crucial for maintaining the integrity and morphology of the tissue, ensuring accurate
histological analysis.
How is Tissue Collected?
Tissues can be collected through various methods depending on the type of tissue and the study's requirements. Common collection techniques include
biopsies, surgical excision, or autopsy. It's vital to use
sterile techniques to prevent contamination and degradation.
What is Fixation?
Fixation is a critical step where tissues are preserved using chemicals to prevent degradation and preserve cellular structure. Common fixatives include
formalin and glutaraldehyde. The choice of fixative depends on the tissue type and the downstream applications, such as
immunohistochemistry or electron microscopy.
Why is Dehydration Necessary?
Dehydration is essential to remove water from the tissue, making it compatible with paraffin or resin embedding. This is typically done through a series of increasing concentrations of ethanol or other dehydrating agents. Proper dehydration ensures that tissues are well-preserved and ready for sectioning.
What is Embedding?
Embedding involves infiltrating the tissue with a medium that provides support during sectioning.
Paraffin wax is commonly used for light microscopy, while resins like epoxy are used for electron microscopy. The embedding medium must be compatible with the tissue type and the intended microscopic technique.
How are Tissues Sectioned?
Sectioning is the process of cutting the embedded tissue into thin slices for microscopic examination. This is performed using a
microtome or an ultramicrotome, depending on the required thickness. Sections for light microscopy are typically 4-5 micrometers thick, while those for electron microscopy are much thinner.
What is Staining?
Staining enhances the contrast of tissues under the microscope, highlighting different cellular components. Common stains include
hematoxylin and eosin (H&E) for general tissue structure, and special stains like PAS for carbohydrates. The choice of stain depends on the specific structures or molecules that need to be visualized.
How are Tissues Mounted?
After staining, sections are mounted onto glass slides with a mounting medium to preserve them for microscopic analysis. The medium must be compatible with the stain used and provide long-term preservation. Coverslips are placed over the sections to protect them and facilitate viewing.
What are the Quality Control Measures?
Ensuring high-quality tissue preparation involves several quality control measures. These include verifying the fixation quality, checking for complete dehydration, ensuring proper embedding, and evaluating the consistency and thickness of sections. Regular quality checks prevent artifacts and ensure reliable results.
Conclusion
Tissue handling and preparation are foundational steps in histology, directly impacting the accuracy and reliability of microscopic analysis. From collection and fixation to sectioning and staining, each step requires meticulous attention to detail. By adhering to best practices and quality control measures, histologists can ensure the integrity of their samples and the validity of their findings.
