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• Histology


  The study of the body organ structure by using the microscope
• Principal or primary types of tissues in the human body

  • Epithelial tissues
  • Connective tissues
  • Muscular tissue
  • Nervous tissue
• Classification of epithelial tissue

  • Covering and lining epithelium
  • Glandular epithelium
• Epithelia


  • They are a collection of cells that form functional unit
  • Most epithelia form a sheet of cells
• Epithelia line most body surfaces, including the skin digestive tract, respiratory tract and all body cavities
• Epithelia form the functional unit and ducts of secretory glands
• Epithelia are the inner lining of all blood vessels and lymphatics
• ~85% of cancers derive from epithelia
• Functions of epithelia


  • Protection
  • Absorption
  • Diffusion
  • Secretion
• Simple epithelium


  A single layer of cells
• Stratified epithelium


  Two or more layers of cells
• Squamous epithelium


  The most superficial layer of cells is flat
• Squamous epithelia


  • They facilitate diffusion of gases and other small molecules
• Cuboidal epithelium


  The cells are about as tall as they are wide
• Columnar epithelium


  The cells are taller than they are wide
• Cuboidal and columnar cells


  • They are usually involved in secretion and/or absorption and need more cytoplasmic volume to accommodate the organelles needed for these activities
• Special types of epithelia

  • Pseudostratified
  • Transitional
• Classification of simple epithelium

  • Simple squamous epithelium
  • Simple cuboidal epithelium
  • Simple columnar epithelium
• Simple squamous epithelium


  • It is a single layer of packed, similar and adhesive cells, which rest on the basement membrane
  • The cells are scale like flattened with centrally located nuclei
  • Found in mesothelium, endothelium and Bowman's capsule
  • The main function is diffusion and lubrication
• Simple cuboidal epithelium


  • It is a single layer of packed, similar adhesive cells, which rest on the basement membrane
  • The cells are square like with spherical and centrally located nuclei
  • Found in the kidney tubules
  • The main function is absorption, secretion and protection
• Basement membrane


  • Separates epithelial cells from surrounding tissue
  • Provides mechanical support by tethering together a sheet of epithelial cells
  • Controls access of epithelia to nutrients, ions, proteins and oxygen
  • Regulates the growth and division of epithelial cells
• Epithelial cells


  • Attached on their basal surface to a basement membrane
  • Lack their own blood supply and rely on the capillaries in the underlying tissues
  • Nutrients from the blood must cross the basement membrane to reach the epithelial cells
• Characteristics of Basement membrane

  • Single layer of packed and adhesive cells which rest on the basement membrane (simple epithelium)
  • Multiple cell layers and only the basal layer rest on the basement membrane (stratified epithelium)
  • The tissue is avascular
  • Epithelial cells are renewed continuously by activity. It can repair and replacement of damaged cells
  • The epithelial cells show polarity
• Epithelial cell surface modifications

  • Microvilli
  • Stereocilia
  • Cilia
  • Flagella
• Adhering junctions


  • Form continuous belt around the circumference of epithelial cells
  • Linked to bundles of actin filaments that also wrap around the cell
  • Myosin filaments can pull on the actin filaments to contract the cell, causing the apical surface to shrink
• Tight junctions


  • Prevent diffusion of molecules between epithelial cells
  • Control the ability of small molecules and ions to diffuse between cells or paracellular diffusion
  • Some epithelia are very permeable (e.g. intestine) where as others are restrictive (e.g. bladder)
• 1. The ciliated cells are present in the simple columnar resorbtive epithelium.

  
  

  YES

  NO

  NO
• 2. The simple squamous epithelium is found in some

  endocrine glands (thyroid glands).

  
  

  YES

  NO

  NO
• 3. The pseudostratified epithelium is usually associated with resorbtion.

  
  

  YES

  NO

  NO
• 4. The stratified squamous keratinizing epithelium originates from the ectoblast.

  
  

  YES

  NO

  YES
• 5. The superficial cells ofstratified squamous non- keratinizing epithelium preserve their nuclei.

  
  

  YES

  NO

  YES
• 6. The simple exocrine glands have a system of branching ducts.

  
  

  YES

  NO

  NO
• 7. The mucous cells contain well developed rough-surfaced endoplasmic reticulum.

  
  

  YES

  NO

  NO
• 8. The regeneration of the simple epithelia is through the substitutive (germiantive) cells localized between the mature epithelial cells.

  
  

  YES

  NO

  YES
• 9. The epithelial tissue is devoid of own blood or lymph vessels.

  
  

  YES

  NO

  YES
• 10. Two parts of the cytoplasm, an apical and basal portion

  are recognized in some epithelial cells.

  
  

  YES

  NO

  YES
• 11. The goblet cells evident in the epithelium oforgans of the digestive system are described as "unicellular glands".

  
  

  YES

  NO

  YES
• 12. The regeneration of the simple epithelia is through the germinative (substitutive) cells that are localized between the mature epithelial cells.

  
  

  YES

  NO

  YES
• 13. Which of the following types is the epithelium of blood and lymph vessels:

  
  

  a/ simple cuboidal epithelium

  b/ simple squamous epithelium

  c/ pseudostratified columnar epithelium

  d/ simple columnar resorbtive epithelium

  b/ simple squamous epithelium
• 14. Which of the following types si the epithelium of lung alveoli:

  
  

  a/ simple cuboidal epithelium

  b/ simple squamous epithelium

  c/ pseudo stratified columnar epithelium

  d/ simple columnar resorbtive epithelium

  b/ simple squamous epithelium