Have you ever wondered where the tissues you study come from?

Some are human tissues, and others are from our more distant cousins. Human sources include surgical specimens and tissue obtained at autopsy.

The methodologies and techniques used in the preparation of tissues for study are extensive and beyond the scope of this course. However, in order to interpret the images observed in the light microscope, a basic understanding of light microscopy tissue preparation and staining mechanisms is essential.

A short video showing how tissues are prepared light microscopy has been prepared by our colleagues at the IU Medical Center and now would be a good time to watch the explanation. The major steps in that process are summarized below.

• Tissue Preparation
  
  1. Tissue removal and sampling.
  2. Fixation (usually with an aldehyde solution).
  3. Dehydration (replace water with alcohol).
  4. Clearing (replace alcohol with solvent - e.g. xylene - miscible with paraffin).
  5. Embedding (paraffin or plastic).
  6. Sectioning on microtome with steel or glass knives.
  7. Staining (use of dyes and electron opaque stains).