Processing Steps Defined. The quick cooling of the wax ensures a small crystalline structure, producing fewer artifacts when sectioning the tissue. Dehydration A. 2. Heating the paraffin wax to a high temperature alters the properties of the wax. Processing 7. The techniques for processing the tissues, whether biopsies, larger specimens removed at surgery, or tissues from autopsy, are described below. • Muscle biopsies: sections containing both transverse and longitudinal planes. This chapter will provide an overview of the steps in the process and the reagents needed to prepare tissue for microscopic evaluation. Tissues embedded in paraffin, which is similar in density to tissue, can be sectioned at anywhere from 3 to 10 microns, usually 6-8 routinely. Tissue processing is concerned with the diffusion of various substances into and out of porous tissues. They differ in the number of carbon atoms within the carbon chain. See more. This course summarizes the most common processing steps utilized in histology today. They should be miscible with both solutions. Isopropyl alcohol is miscible with water, ethanol and most organic solvents. As between Licensee and ICB, the Trademarks, as well as any other trademarks, marks, service marks, trade names, logos, symbols, trade dress, copyrights and/or other intellectual property relating to or used in connection with the Technology and Tissue Processing are, and shall remain, the exclusive property of ICB. If possible, larger and smaller pieces of tissue should be separated and processed using different schedules. The amount of additive will impact the rate of infiltration. Microscopic examination of histological section of the tissue does not always related to normal histology or pathology .processing of tissue specimen is a length procedure. Tissue Fixation. The usual way this is done is with paraffin. A device that prepares tissue samples for sectioning and microscopic examination in the clinical laboratory. Definition: removal of water B. • Infiltrating – permeating the tissue with a support medium. Higher melting point paraffin wax provides better support for harder tissues, e.g. Relate how quality control measures ensure consistent tissue processing and identify tissue that is poorly processed and state a remedy for the problem. It is non-flammable but highly toxic, and produces highly toxic phosgene gas when heated. Conversely, if the molecule size is larger, the rate of exchange is slower (high viscosity). Tissue processing artifacts can include pigments formed by fixatives, shrinkage, washing out of cellular components, color changes in different tissues types and alterations of the structures in the tissue. Select tissue from fixed areas, trim to size and refix until the evening. Automated processors incorporate vertical or rotary oscillation, or pressurized removal and replacement of fluids at timed intervals as the mechanism for agitation. Producing quality slides for diagnosis requires skills that are developed through continued practice and experience. Prolonged treatment with xylene during processing should be avoided, as tissue tends to become overhardened affects the following tissue the most: a. The pink color of the tissue remains during processing, but washes out during subsequent staining. Fixation stabilizes proteins, rendering the cell and its components resistant to further autolysis by inactivating lysosomal enzymes. There are numerous dehydrating agent; ethanol, ethanol acetone, methanol, isopropyl, glycol and denatured alcohols. Tissues from the body taken for diagnosis of disease processes must be processed in the histology laboratory to produce microscopic slides that are viewed under the microscope by pathologists. Picric acid fixatives (Bouin’s) form water-soluble picrates making it necessary to place the tissue cassettes directly into 70% alcohol for processing. If the concentration gradient is excessive, diffusion currents across the cell membranes may increase the possibility of cell distortion. Aim: To process the fixed tissue into a form in which it can be made into thin microscopic sections. For purposes of tissue processing it is used in the same manner as ethanol. The quality of the structural preservation of tissue components is determined by the choice of exposure times to the reagents during processing. Resin is used exclusively as the embedding medium for electron microscopy (see Chapter 22), ultra-thin sectioning for high resolution and also for undecalcified bone (see Chapter 16). Using pressure to increase the rate of infiltration decreases the time necessary to complete each step in the processing of tissue samples. Dehydration – removal of water and fixative from the tissue. For this reason, specimens are processed through a graded series of reagents of increasing concentration. Other reagents affect dehydration by repeated dilution of the aqueous tissue fluids. • Clearing – removal of dehydrating solutions, making the tissue components receptive to the infiltrating medium. Regardless of whether an automated or manual labeling system is used, adequate policies and procedures must be in place to ensure positive identification of the tissue blocks and slides during processing, diagnosis, and filing. The smaller size of the molecules in the solution, the faster the rate of fluid penetration (low viscosity). They are more volatile than the reagent well as immunohistochemistry protocols breast kidney... A lower viscosity in the clinical laboratory action, but may cause difficulty with.. Or calcium may dissolve and leach from tissues are commercially available, providing a selection that is poorly processed state! 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