Stem cells are undifferentiated cells that can renew themselves and differentiate into specialized cell types. There are two main types of stem cells: embryonic stem cells found in blastocysts and adult stem cells found in tissues. Adult stem cells act as a repair system, replenishing tissues through differentiation. In developing embryos, stem cells can differentiate into all cell types but in adults maintain regenerative organs. Sources of adult stem cells include bone marrow, adipose tissue, blood, and umbilical cord blood. Induced pluripotent stem cells are derived from reprogrammed skin or blood cells enabling development of cells for research and therapy.

1. B Y
N A B A A A L W A Z E N
Stem cells

2.  an undifferentiated cell of a multicellular organism
which is capable of giving rise to indefinitely more
cells of the same type,
 and from which certain other kinds of cell arise by
differentiation.

4.  In mammals, there are two broad types of stem cells:
 embryonic stem cells, which are isolated from the
inner cell mass of blastocysts
 adult stem cells, which are found in various tissues.
In adult organisms, stem cells and progenitor cells
act as a repair system for the body, replenishing
adult tissues.


5.  In a developing embryo, stem cells can differentiate
into all the specialized cells—ectoderm, endoderm
and mesoderm
 but also maintain the normal turnover of
regenerative organs, such as blood, skin, or intestinal
tissues.

6.  here are three known accessible sources of autologous
adult stem cells in humans:
 Bone marrow, which requires extraction by harvesting,
that is, drilling into bone (typically the femur or iliac
crest).
 Adipose tissue (fat cells), which requires extraction by
liposuction.
 Blood, which requires extraction through apheresis,
wherein blood is drawn from the donor (similar to a
blood donation), and passed through a machine that
extracts the stem cells and returns other portions of the
blood to the donor.
 Stem cells can also be taken from umbilical cord blood
just after birth

10. Induced Pluripotent Stem Cells (iPS)
 iPSC are derived from skin or blood cells that have
been reprogrammed back into an embryonic-like
pluripotent state
 that enables the development of an unlimited source
of any type of human cell needed for therapeutic
purposes.