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. Author manuscript; available in PMC: 2018 Oct 16.
Published in final edited form as: Birth Defects Res. 2017 Oct 16;109(17):1309–1329. doi: 10.1002/bdr2.1135

Figure 1. Hemochorial placentation.

Figure 1

Schematic diagrams showing placentation sites of the mouse, rat, and human. Similarities and differences exist for each species. The mouse and rat share a trichorial labyrinth zone (LZ), while the human possesses a monochorial villous placenta structure. Labyrinth and villous compartments share functional properties. The mouse exhibits shallow intrauterine trophoblast invasion, whereas the rat and human possess deep intrauterine trophoblast invasion. Invasive and extravillous trophoblast cells are functional equivalents, and the junctional zone (JZ) of the rodent placentation site is homologous to the extravillous column of human placentation. Invasive/extravillous trophoblast cells and natural killer cells direct uterine spiral artery restructuring.