Introduction to Histology Quiz

Introduction to Histology

• Histology is the study of the microscopic structure of cells, tissues, and organs in the body.
• Tissues are composed of two interacting components: cells and extracellular matrix (ECM).
• The study of histology relies on the use of microscopes due to the small size of cells.

Learning Objectives

• Define histology
• Identify the microscope
• Recognize the types of microscopes
• Compare light and electron microscopes
• Identify the principle of preparing histology slides for microscopic examination
• Identify types of staining methods

Microscope

• A microscope is an instrument with magnifying lenses used to examine objects too small to be seen by the human eye.
• Functions include:
  • Resolution: The ability to distinguish fine details
  • Magnification: The ability to enlarge the object
• Resolution of a microscope depends mainly on the quality of its objective lens.
• Resolving power of a light microscope is 0.2 μm
• Resolving power of an electron microscope is 1 nm
• Magnification is only useful when accompanied by resolution.

Types of Microscopes

• Light microscope (LM): uses light passing through thin stained tissue sections.
• Electron microscope (EM): uses electron beams and electromagnetic lenses.
  • Transmission electron microscope (TEM): uses electrons passing through ultrathin tissue sections to study fine tissue structures
  • Scanning electron microscope (SEM): uses an electron beam scanning the surfaces of cells, tissues, and organs to produce a 3-dimensional image.

Preparing Histological Slides

• Thin stained tissue sections must be prepared for microscopic examination.
  • Fixation
  • Paraffin processing
  • Embedding tissues in paraffin blocks
  • Sectioning tissues
  • Staining (H&E, special staining, IHC)

Staining Methods

• General staining methods reveal the general structure of tissues
  • Hematoxylin stains acidic cell components (like DNA and RNA) blue (basophilic)
  • Eosin stains basic cell components (like cytoplasm proteins) pink (acidophilic)
• Special staining methods reveal certain tissue components
  • Sudan Black dye stains lipids
• Histochemical and cytochemical staining methods are specific chemical methods based on specific binding of the dye to a certain tissue component
  • Periodic Acid Schiff (PAS) reaction stains carbohydrates (glycogen)

Main Differences between LM and EM

Self-exam Questions (Examples)

• The two interacting tissue components are cells and extracellular matrix (ECM).
• The study of histology depends on the use of microscopes.
• The two main functions of microscopes are resolution and magnification.
• Electron microscopes are based on the use of a beam of electrons.
• To study tissues by the microscope, sections must be prepared.
• Cell components are stained by acidic dyes.
• Identify types of electron microscopes, microscope functions, and staining methods