During tissue processing, which step follows fixation?

Following fixation in tissue processing, the next critical step is dehydration. Fixation serves to preserve the tissue structure and maintain cellular integrity by cross-linking proteins and halting biochemical processes. Once fixation is complete, the tissue must be dehydrated to prepare it for embedding in a medium such as paraffin. This step involves removing water from the tissue, which is typically done using an alcohol series of increasing concentrations.

Dehydration is essential because most embedding media are not water-soluble. If the tissue remains hydrated, it cannot be efficiently infiltrated by the embedding material, compromising the quality of the sections that will be prepared later. Therefore, dehydration is a crucial step that must occur after fixation to ensure that the tissue is adequately prepared for further processing and effective analysis.