What Are Embryonic and Adult Stem Cells?
Human embryonic stem cells appear in an embryo, a fertilized human egg, five to seven days after conception. They are ordinarily extracted from extra embryos that have been donated for research by parents who tried to conceive a child through certain procedures performed at fertility clinics. Embryonic stem cells have the potential to develop into all cell types of the body. Adult stem cells are obtained for scientific research from many organs and tissues including the brain, bone marrow, blood vessels, skin, and the liver. These stem cells are generally limited to becoming the cell type of its tissue of origin.
