Stem cells are defined by their ability both to self-renew and to give rise to cell types different from themselves. In general, stem cells are classified into two major categories on the basis of their source, namely embryonic stem cells and adult stem cells.
Totipotent embryonic stem cells can be obtained from the blastocyst of mammalian embryos. The blastocyst is a hollow sphere of cells developing on day 4 from early zygotic cells. Blastocysts are usually acquired from unused human embryos produced by in vitro fertilization.
Adult stem cells (postnatal) are found in mature tissues. They are still pluripotent, being responsible for long-life organ regeneration. Plasticity of adult stem cells can generate lineages of cells different from their original organ of origin. Thus, these cells can be used for organ regeneration and for cellular
repair.
Stem cells collected from umbilical cord or bone marrow are considered Adult Stem Cells.
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© 2006 Cryopraxis Cryobiology
