Preparing Microscope Slides For Studies In Schools

By Kenneth Collins


Slides for university students are usually prepared in the histology lab. Students in medical sciences are often trained to know what a tissue is when placed on a slide. The essence is for them to be able to identify anomalies or deviations from the standard ones. However, before they can start taking any of the required lectures, the lab technologists must take the tissues through some histology techniques to prepare microscope slides.

There are different types of microscopes used in the lab. They include the light, electron, fluoresce, phase contrast and confocal microscopes. The one to use depends on the slides to view and how requirements available for using them. These microscopes are also different in several ways.

The parts of a light microscope include the presence of lamp, iris, diaphragm, tube and lenses, eyepiece, adjustment knobs, and objective lens. There are usually three types of adjustment knobs, and they include condenser height, fine and coarse knobs. Their major function is to control the clarity of what is being viewed.

The tissues that will be placed under the microscope must be processed before they can be used. There are different techniques to do this and they include fixation, dehydration, clearing, waxing, embedding, and staining. The use of chemicals applies in these steps and they have to be in the required amount if the tissue is going to be well prepared or last long.

When the cell dies, it is going to start decaying almost immediately but this can be avoided by fixation. Fixation is therefore a step taken to prevent putrefaction so that the tissue can still be useful. Fixatives to use for this purpose include Bouin's fluid, salt, and buffered formalin while alternative methods are refrigeration and heating. When fixatives are used, the volume should be in the proportion of 75 percent to 25 percent. The quantity of the fixative should be more than the tissue so that it can be well soaked.

After fixing, the next step is dehydration. The essence of dehydrating is to remove water from the tissue. To do this, alcohol is used in ascending grades. That is, you can use 50%, 50%, 75%, 75%, 98% and 98% in that order. Maintaining this gradual ascent is important. When dehydration is not done properly, it can cause bubbles to exist and the tissue can distort after shrinking.

After dehydrating the tissue, the alcohol has to be removed and this can be done by the process called clearing. It can be done with clearing agents such as xylene, benzene, toluene, and chloroform. Afterward, impregnate with wax to remove xylene. Apart from removing the xylene, waxing makes cutting easy and the quality of the cuts to be strong.

The wax must also not be allowed to remain. One way of achieving this is by rehydration. Just like alcohol was used in dehydration, it is also used in rehydration, but this time, the different concentrations are used in descending grades. You should start with absolute alcohol and end in 50% alcohol. This can be followed by the use of water. Afterward, the tissue is stained with some dyes that can aid the identification of its components. Examples are Periodic Acid Schiff, Van Gieson, Osmium tetroxde, Masson trichrome and Sudan black.




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