What are Embryotic Stem Cells?

 Embryonic stem cells (ES cells) are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. An embryotic stem cell can divide indefinitely (self renew) and produce any cell in the body (known as pluripotency). The diagram below shows a fertilized egg, grown in vivo, meaning it was grown in a living organism. The blastocyst is only found naturally in embryotic stem cells. It is a modified blastula stage, with consists of an  inner cell mass and a thin trophoblast layer enclosing the blastocystic cavity, which encases the stem cells. The stem cells are extracted from the blastula and grown in vitro, meaning in an artificial environment. Here they can develope into any cell in the body. ES cells, unlike multipotent cells, have the ability to change into any of the three germ layers: ectoderm, endoderm, and mesoderm.

Embryonic stem cells hold the capacity to produce every type of cell and tissue in the body.

"ES cells are derived from the pre-implantation blastocyst, a hollow sphere of cells containing an outer layer of trophoblast cells which give rise to the placenta and the inner cell mass (ICM), from which ES cells are derived. Cells of the ICM ultimately go on to form the embryo proper and therefore have the capacity to form all the tissues in the body. Although these truly pluripotent cells are relatively short-lived in the embryo in vivo, they can be propagated indefinitely in culture in an undifferentiated state."