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Question
Given the correct order of the procedures listed below, to prepare a specimen for microscopic examination.
Given the correct order of the procedures listed below, to prepare a specimen for microscopic examination.
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Solution
The correct option is D Fixation, dehydration, embedding, sectioning, rehydration, staining, mounting.
Light microscopy is the most widely used technique to study the internal details of cells. The sample needs to be properly prepared, cut into thin sections and stained appropriately for viewing in light microscopy. The entire procedure consists of following important preparatory steps.
1. Fixation - aims to preserve the shape of the cells or tissue involved as much as possible.
2. Dehydration- To cut sections, the tissue has to be embedded in paraffin wax, but wax is not soluble in water or alcohol. However, it is soluble in a paraffin solvent called 'xylene'. Therefore, the water in the tissue needs to be replaced with xylene. To do this, first the tissue has to be dehydrated, by gradually replacing water in the sample with alcohol.
3. Embedding- Pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices.
4. Sectioning- The tissue is trimmed, and mounted on a cutting device called a microtome. Thin sections are cut, which can be stained and mounted on a microscope slide.
5. Rehydration- Unfortunately, most staining solutions are aqueous, so to stain the sections, the wax has to be dissolved and replaced with water (rehydration).
6. Staining- enhances colour contrast in visible spectrum. At its simplest, the actual staining process may involve immersing the sample (before or after fixation and mounting) in dye solution, followed by rinsing and observation.
7. Mounting- usually involves attaching the samples to a glass microscope slide for observation and analysis.
Light microscopy is the most widely used technique to study the internal details of cells. The sample needs to be properly prepared, cut into thin sections and stained appropriately for viewing in light microscopy. The entire procedure consists of following important preparatory steps.
1. Fixation - aims to preserve the shape of the cells or tissue involved as much as possible.
2. Dehydration- To cut sections, the tissue has to be embedded in paraffin wax, but wax is not soluble in water or alcohol. However, it is soluble in a paraffin solvent called 'xylene'. Therefore, the water in the tissue needs to be replaced with xylene. To do this, first the tissue has to be dehydrated, by gradually replacing water in the sample with alcohol.
3. Embedding- Pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices.
4. Sectioning- The tissue is trimmed, and mounted on a cutting device called a microtome. Thin sections are cut, which can be stained and mounted on a microscope slide.
5. Rehydration- Unfortunately, most staining solutions are aqueous, so to stain the sections, the wax has to be dissolved and replaced with water (rehydration).
6. Staining- enhances colour contrast in visible spectrum. At its simplest, the actual staining process may involve immersing the sample (before or after fixation and mounting) in dye solution, followed by rinsing and observation.
7. Mounting- usually involves attaching the samples to a glass microscope slide for observation and analysis.
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