Fixation
What is fixation in histology?
Fixation is a critical initial step in
histology where biological tissues are preserved to maintain their structure and prevent degradation. This process stabilizes the tissue, allowing for detailed microscopic examination.
Why is fixation important?
Fixation prevents autolysis and decomposition, ensuring that the tissue’s morphology and cellular details remain intact. It also helps preserve the
antigenicity of proteins for immunohistochemical analysis.
What are common fixatives used?
Common fixatives include
formaldehyde,
glutaraldehyde, and alcohol-based solutions. Formaldehyde is widely used due to its ability to cross-link proteins, thereby stabilizing cell structures.
Embedding
What is embedding in histology?
Embedding involves enclosing the fixed tissue in a solid medium like
paraffin wax or resin, which allows for thin sectioning. It provides structural support to the tissue during slicing.
Why is embedding necessary?
Embedding is essential for obtaining thin, uniform sections of the tissue that can be easily placed on slides for microscopic examination. It also enhances the tissue's durability during sectioning.
How is tissue embedding performed?
The tissue is first dehydrated using a series of alcohol solutions and then cleared with a solvent like
xylene. The cleared tissue is then infiltrated with melted paraffin wax, which hardens upon cooling, embedding the tissue.
Staining
What is the purpose of staining in histology?
Staining adds color to the tissue sections, highlighting different cellular components and structures, which are otherwise transparent. This allows for better visualization and differentiation of tissues under a microscope.
What are some common staining techniques?
How does H&E staining work?
Hematoxylin stains acidic structures like nuclei, while Eosin stains basic structures such as cytoplasmic proteins. This dual staining provides a clear contrast between different cellular components.
Why are special stains used?
Special stains target specific tissue elements, such as connective tissue fibers, carbohydrates, or microorganisms, providing detailed information beyond what H&E staining can offer.
Conclusion
Fixation, embedding, and staining are fundamental steps in histology that ensure the preservation, support, and visualization of biological tissues. These processes are crucial for accurate diagnosis and research, providing insights into the structural and functional aspects of tissues.
