Stem cells

Stem cells in humans

An embryo develops from a fertilised egg. Cells at early stages in the development of the embryo are stem cells.

Stem cells are cells that have not undergone differentiation. A cell which has not yet become specialised is called undifferentiated.

If cells are removed from the embryo - called embryonic stem cells - they will differentiate into any cell type.

Some stem cells remain in the bodies of adults - known as adult stem cells. Adult stem cells are found in limited numbers at certain locations in the body.

Adult stem cells can be found in several regions of the body, including the:

  • brain
  • eyes
  • blood
  • heart
  • liver
  • bone marrow
  • skin
  • muscle

Adult stem cells can differentiate into related cell types only, for instance, bone marrow cells can differentiate into blood cells and cells of the immune system but not other cell types.

Stem cells in plants

Cell division in plants occurs in regions called meristems.

Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.

The main meristems are close to the tip of the shoot, and the tip of the root.

Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.  The main meristems are close to the tip of the shoot, and the tip of the root.

In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated.