Histology

• Histology


  The study of tissues which make up the human body
• Tissue


  A group of cells which perform a common task or function
• Tissue has three components: cells, ground substance (matrix), and fibres
• Basic or principal tissues

  • Epithelium
  • Connective Tissue
  • Muscle
  • Nervous Tissue
• Epithelium


  • Closely packed cells with little or no extra-cellular material
  • Cells are in contact with their neighbours and form continuous sheets or layers
  • Held together by desmosomes and tight junctions
  • Rests on a basement membrane
  • Susceptible to disorders of cellular growth such as cancer
  • One of the few avascular structures in the body
• Epithelial cell shapes


  • Squamous (thin and flat, spread out like a fried egg)
  • Cuboidal (cell height = cell width)
  • Columnar (shaped like a brick)
• Epithelium types


  • Simple Epithelium (one layer of cells)
  • Stratified Epithelium (two or more layers of cells)
• Simple Epithelium types


  • Simple Squamous Epithelium (alveoli in lungs, inner lining of blood vessels)
  • Simple Cuboidal Epithelium (kidney tubules)
  • Simple Columnar Epithelium (inner lining of stomach and intestine)
  • Simple Columnar Ciliated Epithelium (fallopian tube)
• Epithelium continues to regenerate throughout life, making it particularly susceptible to disorders of cellular growth such as cancer
• About 90% of all human cancers are epithelial in origin