What happens during the dehydration step in histological processing?

During the dehydration step in histological processing, excess water is removed from tissues. This step is critical because biological tissues contain a significant amount of water, and in order to properly prepare the tissue for embedding in a medium like paraffin wax, it is essential to eliminate as much moisture as possible. The dehydration process typically involves progressive exposure of the tissue to increasing concentrations of alcohol, which displaces the water effectively.

This dehydration is crucial because the embedding medium must be compatible with the tissue structure and properties. If the tissue remains hydrated, the embedding medium would not adequately infiltrate the tissues, leading to suboptimal sectioning and staining later on. Therefore, this step sets the foundation for high-quality histological preparations, ensuring that the tissues retain their architecture and are suitable for subsequent processes like embedding, sectioning, and staining.