Microtomy & Staining Flashcards

What is the purpose of microtomy in histology?

Answer: To cut tissue into thin slices for viewing under a microscope.

Microtomy is the specialized process of cutting extremely thin sections of embedded tissue using a microtome. This step is essential because tissues need to be thin enough for light to pass through them, allowing for detailed microscopic examination of cellular and architectural features. Without microtomy, the internal structures of the tissue would not be visible or interpretable under a microscope.

Which of the following factors affects the quality of tissue sections during microtomy?

Answer: The cutting speed and knife quality.

The quality of tissue sections during microtomy is significantly influenced by the cutting speed and the sharpness and quality of the microtome knife (blade). An optimal cutting speed prevents chatter or compression artifacts, while a sharp, high-quality knife ensures smooth, even sections without tears or nicks. These factors directly impact the clarity and integrity of the final slide for diagnosis.

What is the most common method of tissue staining in histology?

Answer: Hematoxylin and eosin (H&E) stain

Hematoxylin and eosin (H&E) is the most widely used and fundamental staining method in histology for routine diagnostic purposes. It provides excellent morphological detail, with hematoxylin staining nuclei blue/purple and eosin staining cytoplasm and extracellular matrix pink/red. This combination allows pathologists to easily identify different tissue types and cellular abnormalities, making it indispensable.

What does hematoxylin stain in tissue samples?

Answer: Nuclei

Hematoxylin is a basic dye that has an affinity for acidic components within the cell. In tissue samples, the most prominent acidic structures are the nucleic acids (DNA and RNA) found within the cell nuclei. Therefore, hematoxylin stains the nuclei a distinct blue or purple color, making them easily identifiable and allowing for assessment of nuclear morphology.

Which of the following stains is commonly used for demonstrating collagen fibers?

Answer: Masson's trichrome

Masson's trichrome is a classic special stain specifically designed to differentiate collagen fibers from other tissue components. It typically stains collagen blue or green, nuclei dark brown/black, and cytoplasm/muscle red. This stain is invaluable for assessing fibrosis, connective tissue disorders, and muscle pathology, providing crucial diagnostic information.

What is the role of eosin in tissue staining?

Answer: It stains the cytoplasm pink to red.

Eosin is an acidic dye that binds to basic (eosinophilic) components of the cell, primarily proteins in the cytoplasm and extracellular matrix. In H&E staining, eosin imparts a range of pink to red hues to the cytoplasm, muscle fibers, and connective tissue. This provides essential contrast to the blue-stained nuclei, allowing for clear visualization of overall cellular morphology and tissue architecture.

What is the significance of using a cryostat in histology?

Answer: It freezes tissues for sectioning.

A cryostat is a specialized microtome housed within a freezer cabinet, designed to rapidly freeze fresh tissue samples. This allows for immediate sectioning of unfixed tissue, typically for urgent intraoperative diagnoses (frozen sections) or for studies requiring preservation of heat-sensitive components like enzymes or lipids. Freezing eliminates the need for lengthy chemical processing, providing quick results.

What is the purpose of special staining techniques in histology?

Answer: To visualize specific tissue components or microorganisms.

Special staining techniques go beyond routine H&E to highlight specific cellular structures, extracellular components, or even microorganisms that may not be clearly visible with standard stains. These techniques use specific dyes or chemical reactions to aid in the diagnosis of various diseases, such as identifying specific types of collagen, mucin, or bacteria, providing targeted diagnostic information.

What is the primary purpose of immunohistochemistry (IHC) in histology?

Answer: To detect specific proteins using antibodies.

Immunohistochemistry (IHC) is a powerful technique that utilizes the highly specific binding of antibodies to antigens (proteins) within tissue sections. This allows for the precise localization and identification of specific proteins, such as tumor markers, infectious agents, or cellular differentiation markers. IHC is crucial for accurate diagnosis, prognosis, and guiding treatment selection in pathology.