What does "dehydration" in tissue processing involve?

Dehydration in tissue processing is a critical step that involves the removal of water from the tissue samples. This process is typically accomplished using increasing concentrations of alcohol. The rationale for using alcohol is that it is a non-aqueous solvent that can effectively extract water from the tissue, which is essential for preparing the tissue for subsequent infiltration with embedding media, such as paraffin.

The use of increasing concentrations of alcohol allows for a gradual transition that minimizes cellular damage and preserves the morphological characteristics of the tissue, making it easier to slice thin sections for microscopic examination. Ethanol, isopropanol, or other alcohols are commonly utilized due to their properties that promote dehydration without significant distortion of the tissue architecture.

In contrast, the other options do not accurately represent the dehydration process: saline solutions would introduce water rather than remove it, while adding water does the opposite of what dehydration entails. Creating a vacuum may aid in removing air from the tissues but does not specifically address the removal of water as a high saturation of alcohol does.