Histology and Microscopy Techniques

Histology:

• The study of the microscopic structure of normal tissue.
• Aims to understand the microanatomy of cells, tissues, and organs.
• Focuses on correlating structure with function.

Microscopy in Histology:

• Uses different types of microscopes to study tissues.
• Light microscope (LM): Commonly used, has a resolution power of 0.2µm and a maximum magnification of x1000.
• Electron microscope (EM): Offers higher resolution power (0.2nm) and magnification (x100,000) compared to the LM.
• Resolution power: The ability to distinguish two separate points, measured as the minimum distance needed for them to appear as distinct entities.

Staining Techniques:

• Cells are normally colorless and difficult to distinguish without staining.
• Acidic stains: Stain basic structures, making them appear acidophilic (e.g., eosin).
• Basic stains: Stain acidic structures, making them appear basophilic (e.g., hematoxylin).
• Neutral stains: Combination of acidic and basic stains, suitable for staining blood cells (e.g., Leishman's stain).
• Vital stains: Used to stain living structures within a living organism (e.g., trypan blue or India ink for phagocytic cells).
• Supravital stains: Used to stain living cells outside a living organism (e.g., Brilliant Cresyl blue for reticulocytes).
• Metachromatic stains: Produce a new color upon staining, different from the original stain color, due to a chemical reaction with specific structures within the cell (e.g., toluidine blue stains mast cell granules with violet color).
• Orcein stain: Stains elastic fibers brown.
• Silver stain: Stains reticular fibers brown or black, also used to demonstrate the Golgi apparatus.
• Osmic acid: Stains myelin sheath black.
• Histochemical & cytochemical stains: Used to localize and demonstrate certain substances within a tissue or cell based on biochemical reactions.
  • Glycogen: Stained red by Best's carmine.
  • Lipids (fat): Stained black with Sudan black and orange with Sudan III.
  • Enzymes: Stained using specialized methods (e.g., acid and alkaline phosphatase enzymes).

This quiz focuses on the microscopic study of histology, emphasizing the correlation between structure and function in tissues and cells. It also covers various microscopy techniques and staining methods essential for observing tissue structures. Test your knowledge on light and electron microscopy as well as staining techniques used in histology.