Stem Cells

• Stem cells are unspecialised animal cells involved in growth and repair.

  
  

  • they reproduce themselves indefinitely by mitosis whilst remaining unspecialised

  
  

  • develop into various types of specialised cells when required e.g. to replace dead or damaged cells
• Embryonic stem cells:

  
  

  • found in early embryos

  
  

  • these have the ability to develop into any type of body cell

  
  

  • have the potential to regenerate an entire organ from a few cells
• Tissue/adult stem cells:

  
  

  • found at various locations within a fully formed body e.g. bone marrow, blood and skin

  
  

  • more limited potential than embryonic stem cells

  
  

  • Can only replenish the supply of one or more types of specialised cells i.e. stem cells in red bone marrow can only produce new blood cells.
• Arguments against embryonic stem cell research:

  • Unethical because results in destruction of embryo
  • Some believe that an embryo is a human person. So fatally extracting stem cells is equivalent to murder.
• Arguments for embryonic stem cell research:

  
  

  • Normally the stem cells are obtained in vitro and therefore would be destroyed eventually anyway.
  • Others believe that the ball of cells that make up the 14-day-old embryo is not yet a person and therefore removing cells for research is morally acceptable.
• Human stem cells can be grown in cultures provided they have optimum conditions.
• Marrow in the centre of bones - Treating leukaemia, a type of cancer caused by abnormal blood cells.
• Skin - Growing new layers of skin that can be used to treat burn victims.
• Heart muscle - Repairing damaged heart muscle

  after a heart attack (this is still being tested).
• Bladder - Building a new bladder in a lab for a patient whose bladder has been damaged by injury or disease.
• What is a stem cell? And identify TWO places in the

  human body where stem cells are found?

  An unspecialised animal cell involved in growth and

  repair. Bone marrow and skin.
• Name TWO features of a stem cell that are not exhibited by a ciliated epithelial cell?

  Stem cells, but not ciliated epithelial cells, can

  reproduce themselves by cell division but remain

  unspecialised, develop into various types of

  specialised cell when required to do so.