11. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocoele. 12. However, ultimately, the inner cell mass , inside the trophoblast layer, is aligned closest to the decidua. 13. These embryos were of poor quality, lacking a substantial inner cell mass and poorly constructed trophectoderm. 14. Inside the sphere is a blob known as the inner cell mass , which contains the stem cells. 15. The stem cells are part of an inner cell mass within an embryonic sphere called a blastocyst. 16. The inner cell mass , the embryoblast, begins to transform into two distinct epithelial layers just before implantation occurs. 17. As the syncytiotrophoblast starts to penetrate the uterine wall, the inner cell mass ( embryoblast ) also develops. 18. Further segregation of blastomeres into the trophoblast and inner cell mass are regulated by the homeodomain protein, Cdx2. 19. Embryonic stem ( ES ) cells are the cells of the inner cell mass of a blastocyst, an early-stage embryo. 20. That clump, the inner cell mass , ordinarily consists of stem cells that can be isolated and grown in a laboratory.
