The process of removing water from tissue is called:

• A. Dehydration
• B. Hydration
• C. Clearing
• D. Embedding

Answer: (A)

Removing water from tissue happens during dehydration, where the specimen is passed through increasing concentrations of alcohol to replace water with alcohol. This water removal is essential because alcohol can be easily displaced by the clearing agent that will follow and then allow paraffin to infiltrate for embedding. Hydration would add water back into the tissue, which is not the goal in routine processing. Clearing comes next, using a solvent such as xylene to replace the alcohol, making the tissue ready for infiltration with paraffin. Embedding is the step where molten paraffin infiltrates the tissue to provide solid support for microtomy.