part of part of trophoblast cell chorionic trophoblast cell https://cellxgene.cziscience.com/cellguide/CL_0011101 Cells of the uterine chorion that acquire specialized structural and/or functional features that characterize chorionic trophoblasts. These cells will migrate towards the spongiotrophoblast layer and give rise to syncytiotrophoblasts of the labyrinthine layer. The chorionic trophoblast cell, vital for placental development in mammals, originates from the blastocyst's outer layer, the trophectoderm. As a significant component of the placenta, the chorion forms the external fetal-maternal interface and consists primarily of chorionic trophoblast cells. These cells are pivotal in embryogenesis, fetal nutrition, waste removal, and immune response generation, contributing crucially to the success of pregnancy. Chorionic trophoblast cells undergo trophoblast differentiation, giving rise to specialized sub-types: cytotrophoblasts and syncytiotrophoblasts. Cytotrophoblasts, found in the inner layer, serve as stem cells and contribute to proliferative activities. In contrast, syncytiotrophoblasts, originating from cytotrophoblasts, form the outer layer with a distinctive multinucleated, continuous, and non-proliferative structure. These cells play a key role in maternal-fetal gas and nutrient exchange, producing essential hormones like human chorionic gonadotropin (hCG), progesterone, and estrogen, vital for sustaining pregnancy. Apart from their physiological roles, chorionic trophoblast cells play a crucial role in shielding the fetus from the maternal immune system. They accomplish this by modifying the expression of major histocompatibility complex (MHC) molecules, which are self-identifying proteins utilized by the immune system to identify foreign cells. Through selective expression of specific types of these molecules, trophoblast cells can evade cytotoxic T cells that might otherwise attack them, while still retaining the ability to attract natural killer cells. These natural killer cells assist in trophoblast invasion and the remodeling of blood vessels in the uterus. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) chorion membrane