Fixation (histology)

Fixation (histology) is a process in histology, a branch of anatomy, that involves preserving the structure of cells and tissues for examination under a microscope. This process is crucial in preparing samples for both light microscopy and electron microscopy.

Process

The process of fixation aims to preserve cells and tissue in a 'life-like' state. However, the process can also lead to changes or artifacts, which can be misleading when examined. The two main types of fixation are:

• Chemical Fixation: This involves the use of a fixative, a chemical substance that preserves or fixes tissue samples. Common fixatives include formaldehyde, glutaraldehyde, and osmium tetroxide. The choice of fixative depends on the type of tissue and the specific structures that need to be preserved.

• Physical Fixation: This involves the use of physical methods such as heat or desiccation. An example of physical fixation is heat fixation, often used in bacteriology for preserving bacterial samples on a slide.

Importance

Fixation is a critical step in the preparation of samples for microscopy. It preserves the structural integrity and biochemical composition of the cells and tissues, allowing for accurate study and interpretation. Without proper fixation, cellular structures can degrade or change, leading to inaccurate results.

Techniques

Different techniques are used for fixation, depending on the type of tissue and the structures to be observed. These techniques include:

• Perfusion: This technique is often used for fixation of large tissues or whole organs. The fixative is introduced into the bloodstream to rapidly fix the tissue.

• Immersion: This technique involves immersing the tissue in a container of fixative. It is often used for small tissue samples.

• Freezing: This technique is used for rapid fixation of tissue samples. It is often used in combination with chemical fixation.

See Also

• Histopathology
• Immunohistochemistry
• Microtome
• Staining (histology)