Fixation is one of the most crucial steps in histopathology lab procedures. It is the process of preserving the tissue sample by preventing its degradation and maintaining its morphology and cellular structure. Fixation is essential to ensure accurate diagnosis and proper treatment of diseases.
The primary objective of fixation is to prevent autolysis, which is the breakdown of tissues by their own enzymes. Autolysis can cause significant changes in the morphology of the tissue, making it difficult to identify and diagnose diseases accurately. Fixation also helps in preserving the antigenicity of the tissue, which is essential for immunohistochemistry studies.
There are several types of fixatives used in histopathology labs, including formalin, alcohol, Bouin s solution, and Zenker s solution. Formalin is the most commonly used fixative due to its excellent preservation properties and cost-effectiveness. It works by cross-linking the proteins in the tissue sample, making them resistant to degradation.
Alcohol-based fixatives are used for delicate tissues that are prone to damage during processing. Bouin s solution is used for preserving delicate tissues, such as embryos and fetuses. Zenker s solution is used for preserving tissues that are rich in glycogen, such as liver and kidney tissues.
The duration of fixation depends on the size and type of tissue sample. Small biopsies require shorter fixation times than larger specimens. Under-fixation can lead to poor preservation of the tissue, while over-fixation can cause excessive cross-linking, leading to artifacts that can interfere with diagnosis.
After fixation, the tissue samples are processed through a series of steps that include dehydration, clearing, and embedding in paraffin wax. The paraffin blocks are then sectioned into thin slices using a microtome and mounted on glass slides for staining.
To summarize, fixation is a critical step in histopathology lab procedures that ensures accurate diagnosis and proper treatment of diseases. It is essential to choose the appropriate fixative and duration of fixation to preserve the tissue s morphology and cellular structure. Proper fixation techniques can help in achieving high-quality histological sections for accurate diagnosis and treatment.