Histopathology Clearing Lecture Notes 2024-2023

‫معهد طرابلس العالي للعلوم‬ ‫الطبية‬ ‫فرع زليتن‬ Histopathology Clearing of lecture Hamza altaher aborawi 2024- 2023  INTRODUCTION TO CLEARING OF TISSUES After dehydrating the tissues, the alcohol present in them must...

‫معهد طرابلس العالي للعلوم‬ ‫الطبية‬ ‫فرع زليتن‬ Histopathology Clearing of lecture Hamza altaher aborawi 2024- 2023  INTRODUCTION TO CLEARING OF TISSUES After dehydrating the tissues, the alcohol present in them must be removed before they are impregnated.and embedded with paraffin The Paraffin wax used for embedding is immiscible in.both alcohol and water Thus the alcohol must be replaced by some medium.in which both alcohol and paraffin are soluble The medium needs to be eliminated during wax.impregnation.This treatment is known as Clearing Clearing agent also increases the refractive index of Why is clearing required during processing Clearing is required to remove alcohol from tissues and is replaced by fluid which is miscible with wax with which tissue must be.impregnated Clearing agent is necessary as the dehydrating agents are not miscible with.paraffin Clearing agent is miscible with both.dehydrating agent as well as paraffin wax Why is the process of removing alcohol called as clearing The process is called as clearing because in addition of removal of alcohol, the tissues are rendered translucent because refractive index of clearing agents is approximately.equal to that of tissue proteins Name different clearing agents Benzene Xylene Toluene Choloroform Petroleum ether Oil of wintergreen (Methyl salicylate) Cedar wood oil Carbon tetrachloride Clove oil Dioxane Aniline oil What are the features of good clearing agent Good clearing agent should Remove alcohol quickly -1 Clear quickly without overhardening -2 Should not dissolve out aniline dyes -3 Should not evaporate to quickly in wax bath -4 How much volume of clearing agent is required.More than 10 times the volume of the tissue Which is the most commonly used cleaning agent Xylene What are the advantages of xylene It is cheap and rapid in action Can be used in most of tissues Can be used for both paraffin and celloidin embedding What are the disadvantages of xylene It makes tissues excessively hard and brittle, if the tissue is left for more than 3 hours in xylene It is not suitable for brain and lymphnodes Should be handled with care as it causes dermatitis How do we know whether dehydration is complete or not.Pour the xylene on the tissue section If the dehydration is not complete then the xylene.becomes milky Then the tissue should be placed again in absolute.alcohol Name the reagent used for clearing in tissues for electron microscopy Toluene What are advantages and disadvantages of What are the advantages of chloroform It is excellent clearing agent for nervous tissue, lymph nodes and embryos as it causes little shrinkage It does not harden tissue excessively It is best clearing agent for large blocks Not inflammable What are the disadvantages of choloroform It is expensive and evaporates rapidly from wax both What are disadvantages of benzene Benzene is toxic and highly flammable What are the disadvantages of cedar wood oil Wax impregnation after cedar wood oil is slow and 3 changes are essential Which clearing agent used for making embryos, plants and insects transparent so that their internal structures can be seen Oil of Wintergreen (Methyl salicylate) What is the procedure of clearing After dehydration of tissue, it is immersed in 2 or 3 changes of xylene.At the end of clearing tissue should look transparent