Question

Steps in tissue processing for paraffin sections ? please give detailing long answer

Answer 1

Steps in tissue processing for paraffin sections are

1) Obtaining a fresh specimen

• Fresh specimen can taken from various places.The fixation of specimen has to take place at the site of removal itself or immediatley transport the specimen to the laboratary for the further tests.

2) Fixation

• The fixation of the specimen usually do it with formaldehyde(fixative).This will slowly penetrate into the tissues and make it harden.

3) Dehydration

• Dehydration is carried out by immersing the specimen in a series of ethanol of increasing concentration until it gets pure,water free alcohol is reached.All molecules of the water should be removed.

4) Clearing

• After dehydration the tissue is water free,but still it cannot infilterate it with wax because ethanol are immiscible.So to make it miscible a intermediate solvent has to be used to miscible ethanol and wax.This solvent remove ethanol and wax from the tissues.This process is termed as clearing.

5) Wax infilteration

• After clearing the the tissue can infilterated with a suitable wax.
• The wax formulations have very speculiar physical properties to allow the tissues that are infilterated with these wax to be sectioned to form ribbons and to retain elasticity to be flatten fully when introduced into a warm water bath.

6) Embedding or blocking out

• After wax filteration the specimen is completley infilterated with wax and must be formed into blocks.
• This is carried out using embedding centre (filled with molten wax) and the speciemen placed into it.
• After the specimen oriented intoo the mould a cassete is placed on the top with more wax and placed on a cold plate to make it harden.
• After that the block attcahed with the cassete is removed from the mould and is ready for microtomy.