Making a Microscope Slide
Making a microscope slide starts with the fixation of your biopsy or necropsy specimen. The majority of samples are fixed in 10% neutral buffered formalin. Remember the ratio of sample volume to formalin volume should be at least 1:10. Once the tissues are properly fixed, it is trimmed to fit into a tissue cassette.
Tissue cassettes come in different sizes and colors. For standard cassettes, the tissue should be about “2 nickels” thick. Tissues in the cassettes are stored in formalin and transferred to the histology lab. At the histo lab the cassettes are processed. Processing removes the formalin and water from the tissues and replaces it with wax.
The “wax” tissues are then embedded in wax, and the result is called a “block.” To see video of this process, click below.
A microtome is used to slice sections off the block in the form of a “ribbon.” The microtome can be set to cut at different thicknesses — for instance, 4 microns, or 7 microns.
The delicate ribbon is carefully transferred to a warm water bath. To see a video of this process, click below!
The ribbon floats on the surface and a slide can be placed under the water to lift the section up.
The slide is left to dry, and then it is placed in a dry oven which will gently melt the excess parafin from the section, leaving the section of tissue intact. After removal of the excess wax, the slides can be stained with hematoxilin and eosin. This can be done by hand, or by an automated stainer.
Special stains, such as trichrome stains and Geimsa’s, are handled separately. After slides are stained, the final step is to cover slip them. This can be done by hand or by an automated coverslipper. Too see a video of the auto coverslipper, click below.
