![]() ![]() ![]() The preferred thickness is 4-5 micrometers so that it can be stained and put on a microscope slide for examination. Sectioning: Sectioning involves mounting the specimen on a microtome and cutting it into sections. This step is to be performed with caution if the goal is to perform immunostaining because the paraffin wax will inhibit the penetration of antibodies, and lead to a false result. Įmbedding: Embedding is the process of putting the sample into a paraffin wax or a plastic resin to enhance the process of extracting cellular structures. After ethanol is applied, and following the completion of tissue dehydration, xylene is used to remove the ethanol. It removed water from the sample and further hardens the tissue for eventual light microscopy. ĭehydration: The addition of ethanol accomplishes the dehydration of a sample. Its downside is that it does not preserve kidney tissues well and also distorts mitochondrial structure. Bouin is a fixative used for examining embryo and brain tissue because of its superior preservation of delicate nuclei and glycogen. Its benefit is that it is the fixative of choice for immunostaining however, it requires preparation at the time of the fixation. Paraffin-formalin is another effective fixative. ![]() The fixation step is vital to the rest of the histologic staining procedure because by retaining the chemical composition of the tissue, the sample is hardened and makes the sectioning phase easier. Although several specialized fixatives are available, Neutral Buffered Formalin is a common choice for this step. In modern histology laboratories, most of these steps are automated.įixation: Fixation uses chemicals to preserve the structure of the tissue in its natural form and protects it from degradation by irreversibly cross-linking proteins. For this reason, multiple slides will often be created from a given specimen so that multiple stains can be performed to gather the full range of needed information.īefore specific staining can occur, tissue samples must undergo preparation through the following stages: Fixation, processing, embedding, sectioning, and sometimes antigen retrieval. However, because of its specificity, the other structures will not be seen. The benefit of using a special stain is that it can highlight the specific protein very well. Because of the variety of the proteins that exist, some stains were created to highlight a particular protein, which this review will discuss in the following sections. These two stains are commonly used together to define intracellular organelles and proteins. For example, one of the most common stains, Hematoxylin, is a basic dye that stains proteins a blue color, while Eosin stains proteins a pink color. Each stain exists to highlight an important feature or component within a tissue type. Epithelium, connective tissue, muscle tissue, and nervous tissue have commonalities but look very distinct structurally after staining. Four basic types of human tissue can be stained and viewed using various histological techniques. ![]()
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