Lesson 1 and 2

• Histology


  The study of tissues, in particular, normal tissues

  
• We will be viewing human tissues under the microscope and learning the appearance of these tissues

  
• Cells make tissues and tissues make organs
• Histologist/Histopathologist


  Healthcare professional that performs microscopy to study the structure of normal and abnormal tissues

  
• Histopathology


  The study of abnormal tissues, the counterpart of Histology

  
• Why we need to study the appearance of normal tissues


  • A med tech should have a thorough understanding of the appearance of normal tissues
  • Knowing what a normal tissue looks like will help differentiate it from abnormal tissues

  
• Cytology


  The study of the structure and function of the plant and animal cell
• Organology


  The study of the organs and the organ system
• Objectives of this subject


  • To prepare you for med tech subjects
  • To develop skills in Microscopy
• Microscopy is one of the most basic and essential skill of a medical technologist, and one that a med. tech. should be excellent in
• Brightfield Microscope


  • Routinely used
  • Contains two lens systems for magnifying specimens
  • Specimen is illuminated by a beam of tungsten light
  • Specimen appears dark against a bright background
  • Limitation - absence of contrast between the specimen and the surrounding medium, which makes it difficult to observe living cells
• Darkfield Microscope


  • Similar to the ordinary light microscope
  • The condenser system is modified so that the specimen is not illuminated directly
  • The condenser directs the light obliquely so that the light is deflected or scattered from the specimen
  • The specimen appears bright against a dark background
  • Living specimens may be observed more readily
• Phase-Contrast Microscope


  • Observation of unstained microorganisms is possible here
  • Includes special objectives and a condenser that makes visible cellular components that differ slightly in their refractive index
  • The image appears dark against a light background

  
• Fluorescent Microscope


  • Used most frequently to visualize specimens that are chemically tagged with a fluorescent dye
  • The source of illumination is an ultraviolet (UV) light
  • The ocular lens is fitted with a filter that permits the longer ultraviolet wavelengths to pass, while the shorter wavelengths are blocked or eliminated
  • UV radiations are absorbed by the fluorescent label and the energy is re-emitted in the form of a different wavelength in the visible light range
  • Fluorescent dyes absorb at wavelengths between 230-350 nm and emit an orange, yellow or greenish light
  • Used primarily for the detection of antigen-antibody reactions
• Electron Microscope (EM)


  • Provides a revolutionary method of microscopy
  • Magnifies up to one million
  • Permits visualization of submicroscopic cellular particles and virus
  • The specimen is illuminated by a beam of electrons rather than light
  • Focusing is carried out by electromagnets instead of a set of optics
  • Components are sealed in a tube in wherein a complete vacuum is established
  • Specimens should be thinly prepared, fixed, and dehydrated to allow the electron beam to pass through freely
• Transmission EM


  • Requires specimens that are thinly prepared, fixed, and dehydrated to allow the electron beam to pass through freely
  • As the electrons pass through the specimen, images are formed by directing the electrons onto photographic film - this makes the internal cellular structures visible
• Scanning EM


  • Used for visualizing surface characteristics rather than intracellular structures
  • A narrow beam of electrons scans back and forth, producing a three dimensional image as the electrons are reflected off the specimen's surface
• Parts of a Compound Brightfield Microscope


  • Body Tube
  • Arm
  • Base
  • Mechanical Stage
  • Occular or Eyepiece Lens
  • Illuminator or Light Source
  • Condenser
  • Iris Diaphragm
  • Revolving Nosepiece or Turret
  • Scanner Objective (4X)
  • Low Power Objective (10X)
  • High Power Objective (40x)
  • Oil Immersion Objective (100X)
  • Immersion Oil
• Magnification


  Enlargement or magnification of a specimen is the function of a two-lens system, the ocular lens and the objective lens
• Once the microscope is on the table, remove all unnecessary materials, uncoil the microscope's electric wire and plug into the outlet, clean all lens systems
• After using the microscope, clean all the lenses with a dry, clean lens paper with a drop or two of methanol, place the objective back to LPO, center the mechanical stage, coil the electric wire are the body tube, and return the microscope
• Cell


  Cell is basic unit of life, contains organelles which keeps it functional, cells make tissues, tissues make organs, organs make organ systems, organ systems make organisms
• Two general types of cells


  • Prokaryotic Cells
  • Eukaryotic Cells
• Prokaryotic Cells


  • Small and simple, 0.1 to 5.0 µm in size, unicellular, nucleus is absent, circular DNA, single haploid (n) chromosome, lack membrane-bound organelles, reproduce both sexually and asexually, cell division by binary fission, examples are bacteria and archaea cells
• Eukaryotic Cells


  • Large and complex, 10 to 100 µm in size, unicellular or multicellular, nucleus is present, linear DNA, paired diploid (2n) chromosome, has membrane-bound organelles, mostly reproduce sexually, cell division by mitosis, examples are plant and animal cells, including humans

  
• Similarities between Prokaryotes and Eukaryotes


  • Have cell (plasma membrane
  • Have cytoplasm
  • Have ribosomes
  • Have DNA

  
• Differences between Prokaryotes and Eukaryotes


  • DNA is naked in Prokaryotes, DNA is bound to protein in Eukaryotes
  • DNA is circular in Prokaryotes, DNA is linear in Eukaryotes
  • Usually no introns in Prokaryotes, Usually has introns in Eukaryotes
  • No nucleus in Prokaryotes, Has a nucleus in Eukaryotes
  • No membrane-bound organelles in Prokaryotes, Has membrane-bound organelles in Eukaryotes
  • 70S ribosomes in Prokaryotes, 80S ribosomes in Eukaryotes
  • Binary fission reproduction in Prokaryotes, Mitosis and meiosis reproduction in Eukaryotes
  • Single chromosome (haploid) in Prokaryotes, Chromosomes paired (diploid or more) in Eukaryotes
  • Smaller size (1-5 µm) in Prokaryotes, Larger size (10-100 µm) in Eukaryotes