Free Histotechnician Practice Test
1. Heat fixation should NOT be used for which of the following stains?
a. Capsular staining
b. Gram stain
c. Endospore staining
d. Acid-fast stain
2. Which of the following is NOT a primary purpose of fixation?
a. To prevent putrefaction
b. To prevent autolysis
c. To enhance differences in the refractive indexes of various tissue structures
d. To expose antigen sites for immunohistochemical staining
3. When processing delicate specimens using a standard closed tissue processor, dehydration should be done by which of the following methods to minimize tissue distortion?
a. A graded series of reagents of increasing concentration
b. A graded series of reagents of decreasing concentration
c. A single reagent at a single concentration
d. Delicate specimens do not require a dehydration step
4. Which of the following is an artifact of over-decalcification of bone tissue?
a. The slide appears to be covered in dust
b. Hematoxylin and eosin (H&E) stain shows poor nuclear (basophilic) staining
c. Large holes are present that could be mistaken for vacuoles
d. The tissue shows a "parched earth" cracking appearance
5. When orienting a tissue for embedding, which of the following tissues requires special attention to ensure it is cut in cross section?
c. Fallopian tubes
d. Muscle biopsies
Answers & Explanations
1. A: Most bacteria produce a capsule, or glycocalyx, just outside the cell wall. This capsule is usually made up of polysaccharides. Heat fixation will cause this moist slime layer to shrink, making it difficult to see once stained. Also, heat fixing may cause a bacterial cell to shrink, creating a clear zone around the cell that appears like a capsule when one does not truly exist. Therefore, when staining to view a bacterial capsule, a sample is air-dried and then a negative stain is generally used for visualization.
2. D: Fixation has many purposes including preventing autolysis and putrefaction, enhancing differences in refractive indexes of tissue structures, maintaining proper relationship between cells and extracellular substances, and making the tissue firmer so dissection and cutting is easier. However, fixation can have the downside of masking antigenic sites, resulting in poor immunohistochemical staining.
3. A: Dehydration should be done slowly. If the concentration gradient differs significantly between the inside and the outside of the tissue, the resulting diffusion currents could produce cell distortions. This is why slowly replacing the water through a graded series of reagents of increasing concentration is necessary to maintain proper structure before clearing and subsequent infiltration with a medium such as paraffin.
4. B: The most common problems associated with bone processing are bone dust, under-decalcification, and over-decalcification. When dust created by the saw when sectioning is pressed into the surface of the bone, the resulting slide appears to be covered in dust. Using a saw with a diamond blade can prevent this problem. Under-decalcification makes section cutting very difficult, resulting in fragmentation problems. Over-decalcification results in poor nuclear staining.
5. C: While most tissues are embedded flat, some tissues require special orientation. Tubular structures, such as fallopian tubes, should be embedded in cross section so that the lumen and all layers can be seen. Tissues with an epithelial surface, such as skin, are oriented so that they are cut in a plane at a right angle to the surface.
Last Updated: 04/18/2018