Interpretation of Histological sections Lecturer Farah E. Ismaeel

Of histological slides Preparation

Fixation Small pieces of tissue are placed in solutions of chemicals Preserve by cross-linking proteins and inactivating degradative enzymes Physical & chemical fixation (formaldehyde 37%)

Dehydration Ethanol 70% The tissue is transferred through a series of increasingly concentrated alcohol solutions, ending in 100%, which removes all water Ethanol 80% Ethanol 90% Ethanol 99%

Clearing Alcohol is removed in xylene or other solvents in which both alcohol and paraffin are miscible.

Infiltration & embedding The tissue is then placed in melted paraffin until it becomes completely infiltrated with this substance. The paraffin-infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden

Sectioning Microtome used for sectioning paraffin-embedded tissues for light microscopy 1 and 10 μm thick sections put on glass slides

Staining Using basic dyes to stain acidic components (basophilic) like nucleic acids (BLUE-VIOLET) Using acidic dyes to stain basic components (acidiophilic) like proteins with amino groups PINK Basic dyes that stain basophilic components: toluidine blue, methylene blue & Hematoxyline Acidic dyes stain the acidophilic components: orang G & Eosin Hemotoxylin & Eosin is the most used stain

Hematoxylin only Eosin only H&E

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