Histology Techniques & Technology Flashcards

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

Answer: To detect specific proteins and antigens in tissues.

Immunohistochemistry (IHC) is a powerful technique used in histology to visualize and identify specific proteins or antigens within tissue sections. By using antibodies that bind to these targets, IHC helps diagnose diseases, determine prognosis, and guide treatment decisions, providing crucial information beyond routine staining.

Why is tissue fixation important in histology?

Answer: To prevent tissue decomposition and preserve structure.

Tissue fixation is the critical first step in tissue processing, aiming to rapidly halt cellular metabolism and prevent autolysis and bacterial decomposition. This process stabilizes the tissue's cellular and architectural components, preserving its morphology as close to the living state as possible for accurate microscopic examination.

What is the primary function of a microtome in histology?

Answer: To cut thin tissue sections for microscopic examination.

A microtome is a specialized instrument used in histology to cut extremely thin, uniform sections of embedded tissue. These thin sections, typically 3-5 micrometers thick, are essential for allowing light to pass through and enabling detailed microscopic examination of cellular and tissue structures.

What is the role of special stains in histology?

Answer: To differentiate between cell types and highlight specific tissue components.

Special stains are employed in histology to selectively highlight specific cellular components, microorganisms, or extracellular substances that are not clearly visible with routine H&E staining. These stains aid in the diagnosis of various conditions by differentiating cell types, identifying pathogens, or demonstrating specific tissue structures like collagen, reticulin, or mucin.

What is the purpose of paraffin embedding in histology?

Answer: To make tissue sections easier to cut.

Paraffin embedding involves infiltrating processed tissue with molten paraffin wax, which then solidifies around the tissue. This provides a firm support matrix, making the delicate tissue rigid enough to be cut into very thin, consistent sections with a microtome without tearing or distortion.

What is the role of dehydration in tissue processing?

Answer: To prepare tissues for embedding by removing water.

Dehydration is a crucial step in tissue processing where water is progressively removed from the fixed tissue using increasing concentrations of alcohol. This is necessary because paraffin wax, used for embedding, is immiscible with water, so the tissue must be completely dehydrated before subsequent clearing and infiltration.

What is the significance of staining tissue with hematoxylin and eosin (H&E)?

Answer: It provides contrast for examining tissue structure, with hematoxylin staining nuclei and eosin staining cytoplasm.

Hematoxylin and Eosin (H&E) is the most common staining method in histology, providing excellent morphological detail. Hematoxylin stains acidic components, primarily cell nuclei (blue/purple), while Eosin stains basic components, such as cytoplasm and extracellular matrix (pink/red), creating a clear contrast for microscopic examination.

Which of the following best describes the process of tissue clearing?

Answer: It removes alcohol and prepares the tissue for embedding.

Tissue clearing is the step after dehydration, where alcohol is removed from the tissue and replaced with a clearing agent, such as xylene. This agent is miscible with both alcohol and paraffin wax, making the tissue transparent and preparing it for successful infiltration with molten paraffin.

What is the function of a cryostat in histology?

Answer: To section frozen tissue samples for immediate examination.

A cryostat is a specialized microtome housed within a freezer cabinet, used to rapidly cut thin sections from unfixed, frozen tissue samples. This technique is vital for urgent diagnoses, such as during surgery (frozen sections), as it allows for immediate microscopic examination without the lengthy processing required for paraffin embedding.