the wall of the chorionic cavity, consisting of ectoblast (trophoblast) and mesoblast (extra-embryonic mesoderm). Later forms two types, viz. smooth chorion (chorion laevae) and bushy chorion (chorion frondosum).
The chorion develops into the placenta. Chorionic cells have the same genetic composition as cells of the fetus. Cells of the chorion are sampled during a prenatal diagnostic test called CVS (chorionic villus sampling).
The outermost of the two membranes surrounding the gestational sac that encloses the developing embryo. Separate from the amnion until about 14 weeks of pregnancy, after which the two membranes stick together without intervening fluid. Like the placenta, with which at the margins it is joined seamlessly, derived from trophectoderm. See also: amnion See also: chorionic villus
The cellular, outermost extraembryonic membrane, composed of trophoblast lined with mesoderm. It develops villi about two weeks after fertilization. Villi are the threadlike projections growing in tufts on the external surface of the chorion. At three weeks, it is vascularized by allantoic vessels.
A thick and durable substance which surrounds and encloses the eggs of all species within the order Lepidoptera. With some eggs this substance is smooth whereas with others it is decorated with symmetrical art-like features. This substance is often the first food that the newly emerged larva will have before beginning to eat its host plant.
The chorion surrounds the embryo and other membranes. It consists of two layers: an outer formed by the primitive ectoderm or trophoblast, and an inner by the somatic mesoderm; with this latter the amnion is in contact.
Chorion Limited is an entertainment company based in the United Kingdom. It possesses the rights to the Mr. Men and Little Miss characters and the literary works of Enid Blyton, Raymond Chandler, Agatha Christie, and Georges Simenon.