HT Histology Techniques & Technology 1 — Questions and Answers
Question 1: What is the purpose of immunohistochemistry (IHC) in histology?
- To prepare tissue slides.
- To detect specific proteins and antigens in tissues. (Correct answer)
- To stain tissue sections with basic dyes.
- To preserve tissue samples.
Correct 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.
Question 2: Why is tissue fixation important in histology?
- To stain tissues for better visibility.
- To prevent tissue decomposition and preserve structure. (Correct answer)
- To remove water from the tissues.
- To make tissue easier to cut.
Correct 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.
Question 3: What is the primary function of a microtome in histology?
- To stain tissue sections.
- To cut thin tissue sections for microscopic examination. (Correct answer)
- To fix tissue samples.
- To prepare tissue for embedding.
Correct 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.
Question 4: What is the role of special stains in histology?
- To stain all tissues equally.
- To differentiate between cell types and highlight specific tissue components. (Correct answer)
- To prepare tissues for sectioning.
- To prevent bacterial growth.
Correct 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.
Question 5: What is the purpose of paraffin embedding in histology?
- To preserve tissue samples.
- To make tissue sections easier to cut. (Correct answer)
- To stain tissues for better contrast.
- To maintain tissue clarity.
Correct 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.
Question 6: What is the role of dehydration in tissue processing?
- To make the tissue sections transparent.
- To remove lipids from the tissue.
- To prepare tissues for embedding by removing water. (Correct answer)
- To fix tissue samples.
Correct 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.
Question 7: What is the significance of staining tissue with hematoxylin and eosin (H&E)?
- It stains proteins and carbohydrates.
- It stains tissue fibers.
- It provides contrast for examining tissue structure, with hematoxylin staining nuclei and eosin staining cytoplasm. (Correct answer)
- It enhances the clarity of tissue samples.
Correct 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.
Question 8: Which of the following best describes the process of tissue clearing?
- It removes fixative from the tissue.
- It removes water from tissue samples.
- It removes alcohol and prepares the tissue for embedding. (Correct answer)
- It helps in staining tissue samples.
Correct 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.
Question 9: What is the function of a cryostat in histology?
- To stain tissues.
- To section frozen tissue samples for immediate examination. (Correct answer)
- To fix tissues before processing.
- To preserve tissue samples for long-term storage.
Correct 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.
HT Histology Techniques & Technology 1
What is the purpose of immunohistochemistry (IHC) in histology?