Tissue processing

TOPIC- TISSUE PROCESSING
Defanition
Methods
Conclusion
Reference

1. TISSUE PROCESSING PRESENTED BY, GOPIKA SUKUMARAN CRI

2. CONTENT INTRODUCTION STAGES OF TISSUE PROCESSING RECEIPT AND IDENTIFICTION LABELLING FIXATION DECALCIFICATION DEHYDRATION

3. CONTENT (CONT) CLEARING IMPREGNATION EMBEDDING SECTION CUTTING STAINING MOUNTING CONCLUSION REFERENCE

4. INTRODUCTION Tissue processing is defined as the process of preparing the tissue by embedding it in a solid medium that is firm enough to support it give sufficient rigidity to enable thin sections soft enough to enable the knife to cut the sections with little damage to the knife or the tissue.

5. STAGES OF TISSUE PROCESSING Receipt and identification Labelling Fixation Dehydration Clearing Impregnation Embedding Section cutting Staining Mounting

6. 1.RECEIPT AND IDENTIFICATION S pecimen received have a request form , lists patient information history description of the site of origin. The specimens are given a number for identification

7. 2. LABELLING Should be insoluble Should not contaminate Should not penetrate Should not react Clearly identifiable Eg : India ink, silver nitrate

8. 3.FIXATION Process in which specimen is treated by exposing to fixative for period of time to facilitate the succeeding steps.

9. AIMS OF FIXATION: Prevents putrification and autolysis. Hardens the tissue which helps in section cutting. Acts as a mordant. Increase the optical density.

10. SIMPLE FIXATIVES FORMALIN Commonly used fixative. Prepared by mixing 40% Formaldehyde gas in 100w/v of distilled water. GLUTARALDEHYDE OSMIUM TETRAOXIDE POTTASIUM DICHROMATE MERCURIC CHLORIDE

11. COMPOUND FIXATIVES MICROANATOMICAL FIXATIVES: Used to preserve the anatomy of the tissues. Eg . 10% Formal saline Buffered formalin CYTOLOGICAL FIXATIVES: Used to fix intracellular structures. HISTOCHEMICAL FIXATIVES: Used to demonstrate the chemical constituents of the cell. Eg . Formal saline Cold acetone Absolute alcohol

12. 4 .DECALCIFICATION P rocess of removal of the calcium salts from the specimen. The various agents used are: Nitric acid Hydrochloric acid Formic acid Pictric acid Acetic acid Citric acid

13. 5 .DEHYDRATION Process in which The water content in tissue is completely reduced By passing the tissue through increasing concentrations of dehydrating agents. Various dehydrating agents: Ethyl alcohol Acetone Isopropyl alcohol Dioxane

14. 6 .CLEARING( DEALCOHOLIZATION) It is the procedure where the alcohol in the tissue is replaced by a fluid which will dissolve the wax The various clearing agents used are; Cedar wood oil : The best agent but is expensive. Benzene : It is carcinogenic. Xylene : It is most commonly used. Chloroform : Toxic and expensive.

15. 7 . IMPREGNATION The process in which empty spaces in the tisssue and cells after removal of water are taken up by paraffin wax. Impregnation is done in molten paraffin wax which has the melting point of 56⁰C (54-62⁰C)

16. 8 . EMBEDDING Transferring the dealcoholised tissue to a mould filled with molten wax allowed to cool and solidify.

17. 9 . SECTION CUTTING The prepared blocks are cut or sectioned T hin strips of varying thickness are prepared. The instrument by which this is done is called as a Microtome. TYPES OF MICROTOMES : Sliding Rotary Rocking Freezing Base sledge

18. 10. STAINING Staining of the section is done to bring out the particular details in the tissue under study. Commonly used stain Haematoxylin Eosin

19. 11. MOUNTING Adhesives used for fixing the sections on the slides: Albumin solution Starch paste Gelatin

20. CONCLUSION It is a critical step that needs to be monitored with utmost care. Due to longer processing time, any mistakes alters the tissue, requiring repetition. They should not be under processed or over processed, as it may hamper the tissue details. To get sections of diagnostic value , processing of tissue should be done with approppriate reagents and embedded in suitable embedding medium depending upon type of tissue.

21. REFERENCES Textbook of Oral Histology & Embryology- ORBANS Textbook of Pathology- HARSH MOHAN- Second edition Wikipedia