trophoblaste

The trophoblast is an essential component of the early mammalian embryo, specifically the outer layer of cells of the blastocyst. It plays a crucial role in the implantation of the embryo into the uterine wall and the subsequent development of the placenta. The trophoblast differentiates into two main layers: the cytotrophoblast and the syncytiotrophoblast.

The cytotrophoblast is the inner cellular layer, composed of individual cells with distinct boundaries. These cells are mitotically active and serve as precursors for the syncytiotrophoblast.

The syncytiotrophoblast is the outer, multinucleated layer formed by the fusion of cytotrophoblast cells. It lacks distinct cell boundaries and is in direct contact with the maternal uterine tissue. This layer invades the endometrium, establishing the initial connection between the embryo and the mother. The syncytiotrophoblast is responsible for producing hormones, most notably human chorionic gonadotropin (hCG), which is vital for maintaining the corpus luteum and pregnancy. It also facilitates nutrient and gas exchange between the mother and the developing embryo.

As pregnancy progresses, the trophoblast undergoes further differentiation and organization to form the chorionic villi, which are the functional units of the placenta. These villi increase the surface area for efficient transfer of nutrients, oxygen, and waste products. The trophoblast's ability to interact with and modify the maternal immune system is also critical for preventing rejection of the semi-allogeneic embryo.