Harden Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Harden and links to relevant pages within the course.
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|Step Three: Orient and Position Specimen According to Tissue Type|
After selecting the appropriate mold, you will determine the correct orientation and position for the specimen in the block face. Place a small amount of molten paraffin within the bottom of the mold, and then move the mold with the specimen to the "cold spot." As the thin layer of paraffin begins to cool and harden, you can quickly move the specimen to the desired position. You will then add additional molten paraffin quickly and replace the cassette bottom atop the mold and over the specimen.
|Final Steps: Four Through Seven|
A few quick steps will finish the process once the tissue has been oriented.Step Four: Complete the paraffin blockAdd a small amount of molten paraffin to completely cover the grooves or openings in the plastic of the cassette. This will ensure that the specimen and cassette bottom will harden together into a secure block. Avoid air bubbles from being trapped below the cassette bottom as you replace it. Do this by tipping the mold slightly and pushing the trapped air out. Start at one corner of the mold and press any air outward as you replace the cassette. Step Five: Harden Move the completed block to the large cold plate to harden. Allow the block to completely cool and harden on the cold plate before attempting to remove it from the base mold. The paraffin of the block will usually appear opaque and white when completely cooled. Step Six: Scrape Neatly scrape excess paraffin from the edges of the block to ensure a secure into the block holder of the microtome.Step Seven: Inspect Check the block for any obvious defects, such as cracks or air bubbles, before submitting it for microtomy.
|Review of the Basic Steps for Routine Paraffin Embedding|
StepsDescription1. Open a single cassetteExamine cassette lid and crevices for tissue fragments. 2. Identify specimen/Verify tissue typeExamine and identify the tissue type. Note the number of pieces, cut surfaces, ink, and special instructions. Check legibility of accession number and verify tissue type.3. OrientSelect appropriate size base mold and position the specimen with correct orientation for tissue type. Fill mold with molten paraffin.4. Complete blockReplace cassette bottom and fill with additional molten paraffin.5. HardenAllow the block to completely cool and harden on the cold plate before attempting to remove it from the base mold.6. ScrapeNeatly scrape excess paraffin from the edges of the block to ensure a secure fit into the block holder of the microtome.7. InspectInspect for gross defects, such as air bubbles.
|Place the basic steps for paraffin embedding in the order that they are performed.||View Page|
|Tools and Instrumentation|
The Instrumentation and tools used for paraffin embedding can vary by laboratory. Methods to heat and hold paraffin in the molten state, as well as to harden it by cooling are required. Shown is a typical paraffin embedding center that is used in many clinical histology laboratories.
|Forceps and Other Tools|
Many histologists use forceps and other tools to help them manipulate and position tissue specimens in the desired arrangement. Histologists often have individual preferences for the size and shape of forceps they use. It is recommended that all types of forceps be wiped well between specimens to prevent carry-over contamination. The use of forceps without "teeth" or small grooves at the tip will also help in preventing carry-over. Tissue tampers or stamper can be used to apply pressure evenly on the specimen to help flatten it so that it will harden in one flat plane as the block solidifies. It is essential to make specimens as flat a possible in relationship to the block face for a single, representative section of the entire specimen to be obtained. Forceps and other tools used to manipulate tissue during orientation must be kept warm so that tissue fragments do not adhere to tools as the paraffin on them will begin to solidify on their the surface if they are too cool. Small warming wells are found in most embedding units for the purpose of keeping tools at the necessary temperatures. These wells should be cleaned as frequently as any tools used during embedding, as they can harbor small tissue fragments that can then be transferred to adjacent specimens.
|Cool forceps are recommended for use during paraffin embedding.||View Page|
|Paraffin with a melting point of 55° C has been selected for embedding. When regulating the holding reservoirs in the embedding center, at what approximate temperature should the molten paraffin be regulated? ||View Page|
|Small to Medium Sized Specimens with Multiple Pieces|
Specimens such as curettage, prostate TURP chips, and other irregularly shaped, multiple piece specimens without clear orientation should be arranged in the block face to show as much surface area of the pieces as possible in the final sections. Try to position each of the pieces to point in the same general direction to reduce as much drag as possible during sectioning, since this can reduce section puckering and wrinkling. You must strive to get all the pieces to harden in the same plane so that one complete, representative section can be obtained.
|Regularly Shaped, Medium Sized Pieces|
When embedding medium sized specimens with greater than one piece, locate any inked or cut surface and place all pieces facing in the same direction using these markers.If multiple levels will be cut from the block, select the smallest mold size that will contain the pieces and still allow a border of paraffin on the outside of the specimen. This will make it easier to place more than one section on a slide during microtomy. As with other types of specimens, you will still seek to make sure all the specimens harden in the same plane so that a single representative section is easier to obtain.