- The mesectodermal cell layer covering the blastocyst that erodes the uterine mucosa and through which the embryo receives nourishment from the mother; the cells do not enter into the formation of the embryo itself, but contribute to the formation of the placenta. The t. develops processes that later receive a core of vascular mesoderm and are then known as the chorionic villi; the t. soon becomes two-layered, differentiating into the syncytiotrophoblast, an outer layer consisting of a multinucleated protoplasmic mass (syncytium), and the cytotrophoblast, the inner layer next to the mesoderm in which the cells retain their membranes. SYN: chorionic ectoderm. [tropho- + G. blastos, germ]
* * *tro·pho·blast 'trō-fə-.blast n the outer layer of the mammalian blastocyst that supplies nutrition to the embryo, facilitates implantation by eroding away the tissues of the uterus with which it comes in contact allowing the blastocyst to sink into the cavity formed in the uterine wall, and differentiates into the extraembryonic membranes surrounding the embryo called also trophodermtro·pho·blas·tic .trō-fə-'blas-tik adj
* * *n.the tissue that forms the wall of the blastocyst. At implantation it forms two layers, an inner cellular layer (cytotrophoblast) and an outer syncytial layer (plasmoditrophoblast), which forms the outermost layer of the placenta and attains direct contact with the maternal bloodstream.Trophoblast sampling was the name originally given to the technique now known as chorionic villus sampling.
* * *tro·pho·blast (troґfo-blast) [tropho- + -blast] a layer of extraembryonic ectodermal tissue on the outside of the blastocyst. It attaches the blastocyst to the endometrium of the uterine wall and supplies nutrition to the embryo. From it are derived the chorion and amnion. The inner cellular layer of the trophoblast covering a chorionic villus is called cytotrophoblast and its outer syncytial layer syncytiotrophoblast. The mesoblast, once thought to be trophoblastic, is now traced in primates to the caudal end of the primitive streak. trophoblastic adj
Medical dictionary. 2011.