These cells differentiate into many placental cells types, including extravillous trophoblast cells. Placental site nodules are lesions of chorionic type intermediate trophoblast, usually small. The placenta is made of a folded trophoblast/endometrial epithelial bilayer. This is produced in the trophoblast cells of the placental tissue. There is increased trophoblast proliferation and enlarging of the chorionic villi. The outer layer of the blastocyst consists of cells collectively called the trophoblast. The trophoblasts adhere by penetrating the endometrium, with protrusions of trophoblast cells. Microscopically, these include villi, trophoblast, fetal parts, and background gestational changes in the endometrium. Their counterparts, the proteoglycans, are found around the trophoblast cells of the blastocyst. The blastomeres in the blastocyst are arranged into an outer layer called the trophoblast. Further, the decidua has to allow a very controlled invasion of the trophoblast. The trophoblast gives rise to the placenta. Specifically, PGF plays a role in trophoblast growth and differentiation. The external, surrounding cells develop into the trophoblast cells. Knocking out mTORC1 results in embryonic lethality due to lack of trophoblast development.