Column Cytotrophoblast Layer

The column cytotrophoblast layer is the middle of three layers of the human placenta (and is analogous to the mouse spongiotrophoblast layer). The chorionic villi layer (analogous to the mouse placental labyrinth layer) is the innermost layer and the extravillous cytotrophoblast layer (analogous to mouse trophoblast giant cell layer), which makes up the outermost layer of the human placenta. During implantation of the embryo into the maternal decidua, invading extravillous cytotrophoblasts leave the basement membrane of the villi to form columns of unpolarized cells that attach to, and then penetrate, the uterine wall. The ends of the columns terminate within the superficial endometrium, where they give rise to invasive endovascular or interstitial cytotrophoblasts.