OSMT (Ontario Society of Medical Technologists) Practice Exam

What is the correct order of tissue processing?

1. a. Fixation, decalcification, dehydration, clearing and embedding

2. b. Decalcification, fixation, clearing, dehydration and embedding

3. c. Decalcification, fixation, dehydration, clearing and embedding

4. d. Dehydration, fixation, clearing, decalcification and embedding

The correct answer is: a. Fixation, decalcification, dehydration, clearing and embedding

The correct sequence for tissue processing begins with fixation, which is crucial for preserving the tissue structure and preventing decay. Fixation stabilizes cellular components and maintains the morphology of the tissue, which is essential for accurate analysis. Following fixation, decalcification is performed if the tissue contains bone or calcified materials. This step is necessary to soften the tissue before further processing. Next, dehydration is carried out. In this process, water is removed from the tissue, typically through a series of alcohol solutions. This step prepares the tissue for the clearing process. Clearing is then done, in which the dehydrating alcohol is replaced with a substance that is miscible with both the embedding medium and the dehydrating agent. This prepares the tissue for infiltration with the embedding medium. Finally, embedding involves infiltrating the tissue with a medium that solidifies, providing a supportive structure for sectioning the tissue into thin slices for microscope examination. This sequence is essential for preparing high-quality specimens for histological analysis, making choice A the correct order of tissue processing.