Basic Tissue Processing for Routine Light Microscopy Assignment

Basic Tissue Processing for Routine Light Microscopy - Assignment Example hnique as the tissues are fixed by cross linkages formed by proteins and the cross links does not harm the protein structure and the standard solution is 10% neutral buffered formalin. Glutaraldehyde is also used for fixation and the standard solution is 2% buffered glutaraldehyde. This causes deformations in protein structure and penetrates very slowly but provides overall cytoplasmic and nuclear detail. Alcohols are usually not used for tissues as contain protein denaturants and cause brittleness. Oxidizing agents such as potassium permanganate is also not used frequently as they cross link proteins and cause extensive denaturation. There are number of factors which affect the fixation process such as buffering, penetration, temperature, volume, time interval and concentration of the solutions. Once the tissue has been fixed, they are processed into thin microscopic sections and embedded in paraffin. The technique of fixing tissues into paraffin is called tissue processing. There a re two main steps in the processing which is dehydration and clearing. ‘Dehydration’ is a process of removing water from the tissues as wet fixed tissues cannot be directly infiltrated with paraffin. This is done by mixing alcohol (70%, 95% to 100%) with formalin. Once the tissues are dehydrated, the next step consists of removal of dehydrant with the substance that will be miscible with the paraffin. The common clearing agent used for this step is xylene. The next step involved is that the tissues are finally infiltrated with the embedding agent paraffin. ‘Infiltration’ is a process of impregnating the tissues with the embedding medium. This processed can be automated for large amount of tissues are processed. Automation consists of an instrument that moves through the tissues on a preset time. This activity can also be done with the help of tissue processor by manually picking the tissues out of the cassette and pouring paraffin over them. This ‘emb edding’ process is very