Stem Cells - Brutes or Angels: Human Possibility in the Age of Biotechnology - page 37

fig. 2.2. Left, blastocyst-stage embryo characteristic of humans and other mammals, showing its two components, the trophectoderm, comprised
of trophoblast cells, and the inner cell mass. in blastocysts implanted in the uterine wall, the trophectoderm forms the fetal portion of the
placenta, and the inner cell mass eventually develops into the fetus. Right, four- to ive-day-old human blastocyst. Photograph by eve feinberg,
fertility Centers of illinois, highland Park, il, used with permission.