Dehydration of Tissue in Histopathology Lab

 Dehydration of Tissue in Histopathology Lab

Removal of Water

First, the tissue needs to be dehydrated to remove the water, which is present either free or bound to the tissue. Paraffin wax is hydrophobic; therefore, most of the water in the tissue must be removed before it can be infiltrated with wax.

 

Removing the water is carried out by immersing tissue in a series of ethanol solutions of increasing concentrations until 100%, water-free alcohol is reached.

 

A series of increasing concentrations is used to ensure that the water in the tissue is gradually replaced by the alcohol and to avoid excessive distortion of the tissue.

Various components of the cell are also removed by this process. At the lower end of the ethanol concentrations, water-soluble proteins are removed, while towards the 100% ethanol step, certain lipids may be dissolved.

Ethanol and Wax Don’t Mix

Although the tissue reaches the final stage of dehydration in 100% ethanol, it’s not possible to proceed straight to wax embedding, as ethanol and wax don’t mix!

This is where tissue clearing comes in. The term clearing refers to the property of the solvents used—they have a relatively high refractive index, and when tissue is immersed in it, it becomes transparent and clear.

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