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Human embryonic stem cells
A: Cell colonies that are not yet differentiated.
B: Nerve cell






Embryonic stem cells

Human embryonic stem cell colony

Embryonic stem cells (ES cells) are stem cells taken from the inner cell mass of the early stage embryo called a blastocyst. Human embryos reach the blastocyst stage 4-5 days after fertilization. At that time, they are made up of between 50 and 150 cells.


Adult stem cells

Adult stem cells exist throughout body after embryonic development has completed. They are found inside different types of tissue and remain in a non-dividing state until disease or tissue injury. They have changed permanently into specialised cells and have lost the ability to divide and specialise further. An advantage of adult stem cells is that it provides a lesser probability of rejection. A disadvantage would be that there is a limited availability to get them.

Plant stem cells

Plant stem cells are unspecialised, and can develop into any type of plant cell. They become specialised into cells of roots, leaves or flowers. The stem cells are found in meristem, at root and stem apices. They make it possible for growth to continue.

Cloning plants

These are plants which have been grown from cuttings (therefore the same plant). They are dipped in hormone rooting powder to develop bigger root systems. They turn into tissues (eg. xylem and phloem) and organs (eg. roots, leaves and flowers), therefore becoming a completely new plant.

Cloning plants is a cheap way of producing a new plant.

Stem cells in medicine

Some cancers may be treated by stem cells. Leukemia, a cancer of white blood cells (WBC) is an example.

There are two stages to this process:

  • Chemotherapy and radiotherapy to kill cancerous white blood cells and stop the production of more. However, this may leave the patient with a severely compromised immune system with a risk of infection.
  • A transplant of bone marrow containing healthy stem cells (to produce normal WBC).

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