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. Author manuscript; available in PMC: 2013 Nov 21.
Published in final edited form as: Syst Biol Reprod Med. 2010 Apr;56(2):10.3109/19396360903431638. doi: 10.3109/19396360903431638

FIGURE 1.

FIGURE 1

Preimplantation development. Preimplantation development takes place between fertilization and implantation and encompasses essential events such as zygotic genome activation, epithelialization/compaction, and the determination of the TSC and ESC lineages of stem cells for the placenta and the embryo. Preimplantation development encompasses the first seven cell divisions and results in the production of determined stem cells for the embryo and extraembryonic yolk sac endoderm and placental lineages. Soon after implantation a subpopulation of TSC differentiates to trophoblast giant cells to produce the first placental hormone placental lactogen (PL)l that contributes to sustaining the corpus luteum and the life of the conceptus. This requires upregulation of heart and mesoderm induced (Hand)1 and downregulation of the related basic helix loop helix transcription factor Inhibition of Differentiation (ID)2.