What Are Human Embryonic Stem Cells and Why Are They Used for Research?
In the final years of the twentieth century, embryo stem-cell research, in particular, became a matter of great interest. Stem cells are cells that develop very early in the human embryo after fertilization. They form the “inner cell mass” of the early embryo during the blastocyst stage, when the embryo is about to implant in the womb (the “outer cells mass” of the blastocyst are called the trophoblast and form the placenta and other supporting and vital organs needed for the development of the unborn child within the mother). These cells go on to form the body of the developing human person and are thus called the embryonic stem cells. Although they are not “totipotential,” as are the cells organized into a unitary whole in the pre-implantation embryo, they are “pluripotential” since they have the capacity to develop into any of the 200 and more different kinds of cells that make up the adult human body. In theory, if these cells are extracted early enough during embryonic life, they
