Histology Chapter 1 Flashcards

Overview of Histology

• Histology is the study of tissues in plants and animals, emphasizing the principle of complementarity where structure and function are interrelated.

Histopathology

• Histopathology involves microscopic examination of diseased tissues, connecting compromised functions with abnormal cellular structures.

Tissue Preparation Artifacts

• Artifacts are structural abnormalities caused during tissue preparation, often appearing as tissue folding.

Steps of Tissue Preparation

• The preparation of tissue slides involves eight critical steps:
  • Fixation
  • Dehydration
  • Clearing
  • Infiltration
  • Embedding
  • Sectioning
  • Mounting
  • Staining

Fixation

• Fixation preserves tissue architecture and kills cells to maintain structural integrity.

Dehydration

• Dehydration entails the removal of water from tissues using a gradient of alcohol solutions.

Clearing

• Clearing replaces alcohol with a solvent compatible with the embedding medium.

Infiltration

• Infiltration involves saturating the tissue with a liquid embedding medium.

Embedding

• Embedding allows the infiltrated tissue to harden and maintain its shape for sectioning.

Sectioning

• Sectioning utilizes a microtome to slice embedded tissue into thin sections for mounting.

Mounting

• Tissue sections are placed on glass slides for examination.

Staining

• Staining enhances tissue contrast and coloration, vital for visual differentiation during microscopy.

Preventing Artifacts

• To minimize artifacts from cell shrinkage, frozen tissue can be sectioned using a cryostat.

Staining Affinities

• Basophilic staining targets basic cationic dyes, primarily highlighting cell nuclei.
• Acidophilic staining shows affinity for acidic anionic dyes, typically coloring cytoplasm.

Common Dyes

• Hematoxylin, derived from logwood, stains nuclei and acidic structures in shades of blue, purple, or black.
• Eosin is a synthetic dye that imparts red or pink hues to cytoplasm and other basic elements.

Microscopy Techniques

• Hematoxylin and eosin (H&E) are the most frequently employed dyes in bright-field microscopy.
• Enzyme histochemistry enables specific enzyme location and activity visualization using fresh frozen tissue and marker compounds.
• Basic components of microscope systems include illuminating systems, specimen holders, imaging systems, and translation systems.

Immunohistochemistry

• Immunohistochemistry employs labeled antibodies to detect specific antigens.
• Direct immunohistochemistry uses a labeled antibody for antigen targeting.
• Indirect immunohistochemistry involves an unlabeled primary antibody that binds to an antigen, followed by a labeled secondary antibody.

Compound Light Microscopes

• Key components include an illuminating system, condenser, objective lens, and eyepiece.
• Bright-field microscopy is the most commonly used type.

Advanced Microscopy

• Phase-contrast microscopy capitalizes on refractive index differences for structural differences.
• Fluorescence microscopy utilizes UV light to view specimens, often those treated with immunohistochemical methods, effectively differentiating nucleic acids like DNA and RNA.