Microscopy

• What do simple squamous epithelium look like?


  Large, thin & flat (1 layer)

  Rounded nucleus

  
• What do simple columnar epithelium look like?


  Single layer of long cells- oval shaped nuclei

  
• Simple columnar epithelium photo:

  
• Simple squamous epithelium photo:

  
• Simple cuboidal epithelium photo:

  
• What do simple cuboidal epithelium look like?


  Large, rounded

  
• What do stratified squamous epithelium look like?


  Layers of squamous cells

  
• What do pseudostratified columnar epithelium look like?


  Single layer of cells with varying heights, giving the appearance of multiple layers.

  
• Stratified squamous epithelium photo:

  
• Pseudostratified columnar epithelium photo:

  
• Why are tissue sections stained?


  To enhance contrast
• What stains are used?

  • Haematoxylin & eosin (H&E)
  • Trichome
  • Heavy metal compounds (e.g, phosphotungstic acid & osmium tetroxide)
• Haematoxylin & Eosin:


  • H stains acidic nuclei purple
  • E stains basic cytoplasmic proteins pink
• Trichome:


  Enhance various components of ECM of bone & cartilage
• How can we work out which cell type is shown in an image?


  For example:

  
• What is gross anatomy?


  Study of structures visible to human eye

  e.g, blood vessel (5mm) or kidney (12cm)
• What is microscopic anatomy?


  Studying structures not visible to naked eye (cells & organelles)
• What is the standard unit of length that scientists use?


  Metres
• What is resolution?


  Minimum distance between distinguishable structures in an image
• Light microscopy:


  • Visualise structures in thin sections of tissue (5-8 micrometres)
  • Resolution 0.2-0.6 micrometres
  • Tissues frozen or fixed in formalin & then embedded in paraffin/resin before sectioning
  • Sections stained to enhance contrast
• What is transmitted light microscopy?


  Microscopy where light transmitted from a source on opposite side of specimen to objective lens
• How does transmitted light microscopy work?


  • Light passed through condenser- focuses it on specimen to give bright image easy to see
  • After passing through specimen, light goes through objective lens- gathers light from specimen & focuses light to produce magnified image of specimen
  • Image passes to eyepiece (ocular) where it's magnified further & viewed
• What is electron microscopy?


  • Uses beam of electrons focused by magnets (not photons) to visualise tissue sections
  • Black & white images produced
  • 2 types: TEM & SEM
• Transmission electron microscopy (TEM):


  • Higher resolution than light microscopy
  • Details ultrastructure/fine structure of cells, tissues & viruses
• Scanning electron microscopy (SEM):

  • View surface of structures
  • Resolution less than 1nm
  • Excellent depth of focus
  • Cryofracture technique creates 'surfaces' at boundaries of anatomical features rather than perfect flat planes
  • Tissue block covered in gold & electrons reflected off surface features
• How are tissue sections cut?


  0.1 micrometres thick