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Embryonic stem cell
Embryonic stem cells
(
ES cells
) are
pluripotent
stem cells
derived from the
inner cell mass
of a
blastocyst
, an early-stage preimplantation
embryo
. Human
embryos
reach the
blastocyst
stage 4–5 days post
fertilization
, at which time they consist of 50–150 cells. Isolating the
embryoblast
or
inner cell mass
(ICM) results in destruction of the blastocyst,
which raises ethical issues
, including whether or not embryos at the pre-implantation stage should be considered to have the same moral or legal status as more developed human beings.
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