What are the types of Stem Cells?
Stem cells can be Embryonic (derived from
embryos created in the lab) or Adult Stem Cell. An Adult Stem cell is found
among the differentiated cells of an organ or tissue that can regenerate
itself.
Adult
Stem Cells
An adult
stem cell is thought to be an undifferentiated
cell, found among differentiated cells in a tissue or organ that can
renew itself and can differentiate to yield some or all of the major
specialized cell types of the tissue or organ. The primary roles of adult stem
cells in a living organism are to maintain and repair the tissue in which they
are found. Scientists also use the term somatic
stem cell instead of adult stem cell, where somatic refers to cells of
the body (not the germ cells, sperm or eggs).
Adult stem
cells have been identified in many organs and tissues, including brain, bone
marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart,
gut, liver, ovarian epithelium, and testis. They are thought to reside in a
specific area of each tissue (called a “stem cell niche”). In many tissues,
current evidence suggests that some types of stem cells are pericytes, cells
that compose the outermost layer of small blood vessels. Stem cells may remain quiescent
(non-dividing or dormant) for long periods of time until they are activated by
a normal need for more cells to maintain tissues, or by disease or tissue
injury.