stem cells

• stem cells

  -all cells begin as undifferentiated cells, they are not adapted to any particular function. (specialised)

  -they have potential to differentiate.

  -undifferentiated cells= stem cells.

  -stem cells can undergo cell division again and again.

  -they are the source of cells necessary for growth, development and tissue repair.

  once stem cells are specialised they enter Go phase of cell cycle

  -uncontrolled division form masses of cells called tumours.
• stem cell potency

  = a stem cells ability to differentiate into different cell types.

  • totipotent= stem cells that can differentiate into any type of cell.
  • pluripotent= stem cells that can form all tissue types but not whole organisms.
  • multipotent= stem cells that can only form a range of cells within a certain types of tissue.
• differentiation

  cells have adapted to different roles in an organism, so have many shapes and contain different organelles.

  • when cells differentiate they become adapted to their specific role. What form this adaptation takes place is dependent on the function of the tissue, organ and organ system.
• sources of stem cells

  -embryonic stem cells= totipotent, early stage of embryo development. After about 7 days a mass of cells (blastocyst) has formed and cells are now pluripotent state and remain like this in fetus till birth.

  -adult stem cells= found in bone marrow- multipotent. Harvested from umbilical cord. can be stored in case they are needed.

  -meristems= found in roots and tips of shoots. in between xylem and phloem.
• uses of stem cells

  -treatment of burns= stem cells grown on biodegradable meshes can produce new skin for burn patients.

  -drug trials= new drugs can be tested on cultures of stem cells before being tested on animals and humans.