Week 1 - intro, staining, and techniques

Why is understanding normal histology essential?

To recognize abnormal, diseased structures.

What are the four basic tissues studied in veterinary histology?

Epithelium, connective tissue, muscle, and nervous tissue.

What is the most common procedure used in histology?

Preparation of thin sections of tissue for light microscopy.

What conditions must a specimen meet for microscopy?

Well preserved, sufficiently thin, and enough contrast.

What are the four major steps of slide preparation?

Fixation, embedding, sectioning, staining.

What is fixation and why is it important?

Preservation of tissues (commonly with 10% buffered formalin) to prevent autolysis and decomposition.

What is embedding?

Fixed tissues are dehydrated and embedded in paraffin for sectioning.

What is sectioning?

Cutting tissues into thin slices (5–10 µm) with a microtome.

What is staining?

Applying dyes to enhance visualization of cellular components.

What is the most commonly used histological stain?

Hematoxylin and Eosin (H&E).

What does hematoxylin stain?

Negatively charged DNA and RNA (nuclei); basophilic structures.

What does eosin stain?

Positively charged cytoplasmic components; acidophilic structures.

What is Masson’s Trichrome used for?

Differentiates connective tissue (collagen = blue, muscle = red, nuclei = dark brown).

What is Verhoeff’s Elastic Stain used for?

Stains elastic fibers black, nuclei grey-black, collagen red.

What does Toluidine blue stain?

Acidic components (nucleic acids) blue, polysaccharides purple (metachromasia).

What does Prussian blue show?

Iron (Fe) deposits.

What does Congo Red stain detect under polarizer?

Amyloid protein aggregates.

Which stains are used for bacteria?

Gram stain (Gram+ purple, Gram– red).

Which stains are used for fungi?

Silver stains (GMS, Gomori), PAS (fungal walls, glycogen, mucins).

What is bright-field microscopy?

Standard LM; condenser focuses light, objective and eyepiece magnify image.

What is fluorescence microscopy?

Uses UV light; shows fluorescent-labeled molecules for specific localization.

What is phase-contrast microscopy?

Allows examination of unstained, living cells.

What is confocal microscopy?

Visualizes specimens in 3D using aligned lenses.

What is polarizing microscopy?

Uses polarized light to observe anisotropic structures.

What is electron microscopy (EM)?

Uses electron beams for higher resolution than LM. Two types: TEM (transmission) and SEM (scanning).

What are the requirements for specimens in microscopy?

Preservation, thin sections, and contrast.

What is immunohistochemistry (IHC)?

Uses antibodies to detect specific proteins in tissues, visualized with fluorophores or chromogens.

What are polyclonal antibodies?

Mixed antibodies from animals (rodents, rabbits, goats, horses).

What are monoclonal antibodies?

Identical antibodies from immortalized cells (myeloma).

What is in situ hybridization (ISH)?

Uses labeled DNA/RNA probes to localize genetic sequences in tissues.

What is cytology?

The study of the anatomy, physiology, pathology, and chemistry of the cell.

Who discovered and named the cell?

Robert Hooke in 1665.

What is the cytoplasm?

Cytosol + organelles.

What are the main transport mechanisms?

Diffusion, channels, carriers/pumps, vesicular transport (endo-, phago-, pinocytosis).

What are microvilli?

Apical projections that increase surface area (e.g., intestinal mucosa).

What is the glycocalyx?

Carbohydrate coating on cells, prevents adhesion (e.g., endothelium).

What are intermembranous junctions?

Cell-cell connections (e.g., desmosomes in epidermis).

What are the main functions of mitochondria?

Oxidative phosphorylation, respiratory chain, Krebs cycle, autonomous division.

Which cells lack mitochondria?

Prokaryotes

What is the rough ER (RER)?

Studded with ribosomes; synthesizes proteins for export

What is the smooth ER (SER)?

No ribosomes; synthesizes lipids, steroids, glycogen metabolism.

What is the Golgi apparatus?

Modifies, stores, and exports proteins and lipids; forms lysosomes.

What are lysosomes?

Organelles full of enzymes for digestion; abundant in neutrophils and renal tubules.