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chorion
cho·ri·on C0327400 (kôr′ē-ŏn′)n. The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta.
[Greek khorion; see gherə- in Indo-European roots.]
cho′ri·on′ic (-ŏn′ĭk) adj.chorion (ˈkɔːrɪən) n (Anatomy) the outer of two membranes that form a sac around the embryonic reptile, bird, or mammal: contributes to the placenta in mammals. See also amnion[C16: from Greek khorion afterbirth] ˌchoriˈonic, ˈchorial adjcho•ri•on (ˈkɔr iˌɒn, ˈkoʊr-)
n. 1. the outermost of the membranes enclosing the embryo in reptiles, birds, and mammals, developing into part of the eggshell or part of the placenta. 2. a membrane enclosing the shell of an insect egg. [1535–45; < Greek chórion afterbirth] cho`ri•on′ic, cho′ri•al, adj. cho·ri·on (kôr′ē-ŏn′) The outer membrane that encloses the embryo of a reptile, bird, or mammal. In mammals, the chorion contributes to the development of the placenta.chorionThe embryo’s outer membrane, which helps to form the placenta.Thesaurus| Noun | 1. | chorion - the outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals)amniote - any member of the Amniotachorionic villus - one of the tiny villi that stick out of the fetal chorion and combine with the mother's uterine tissue to form the placentamammal, mammalian - any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milkfetal membrane - any membrane that functions for the protection or nourishment or respiration or excretion of a developing fetussac - a structure resembling a bag in an animal |
TranslationsSee Chorion
Chorion
Chorion The outermost of the several extraembryonic membranes in amniotes (reptiles, birds, and mammals) enclosing the embryo and all of its other membranes. The chorion, or serosa, is composed of an outer layer of ectodermal cells and an inner layer of mesodermal cells, collectively the somatopleure. Both layers are continuous with the corresponding tissue of the embryo. The chorion arises in conjunction with the amnion, another membrane that forms the outer limb of the somatopleure which folds up over the embryo in reptiles, birds, and some mammals. The chorion is separated from the amnion and yolk sac by a fluid-filled space, the extraembryonic coelom, or body cavity. In those mammals in which the amnion forms by a process of cavitation in a mass of cells, instead of by folding, the chorion forms directly from the trophoblastic capsule, the extraembryonic ectoderm, which becomes gradually underlain by extraembryonic mesoderm. In reptiles and birds the chorion fuses with another extraembryonic membrane, the allantois, to form the chorioallantois, which lies directly below the shell membranes. An extensive system of blood vessels develops in the mesoderm of this compound membrane which serves as the primary respiratory and excretory organ for gaseous interchanges. In all mammals above the marsupials, the chorion develops special fingerlike processes (chorionic villi) extending outward from its surface. To a varying degree in different species of mammals, the villous regions of the chorion come into more or less intimate contact with the uterine mucosa, or uterine lining, of the mother, thereby forming the various placental types. See Allantois, Amniota, Fetal membrane, Germ layers Chorion (1) The outermost embryonic membrane of birds, reptiles, and mammals (including human beings) that is formed in the early stages of development; also called serosa. The embryo receives oxygen from the environment through the chorion, and the embryo of mammals also receives food and eliminates metabolites and carbon dioxide through the membrane. In birds and reptiles, the chorion fuses with the allantois to form a common chorioallantoic membrane next to the eggshell. The chorion of mammals, including humans, is covered with villi, into which the blood vessels of the embryo grow. The villi penetrate into the uterine wall, where they form the placenta. (2) A secondary eggshell of invertebrates and some lower vertebrates. chorion[′kȯr·ē·än] (embryology) The outermost of the extraembryonic membranes of amniotes, enclosing the embryo and all of its other membranes. chorion
chorion [kor´e-on] an extraembryonic fetal membrane, composed of trophoblast lined with mesoderm; it develops villi, becomes vascularized, and forms the fetal part of the placenta.chorion frondo´sum the placental part of the chorion; it is covered by villi.chorion lae´ve the nonvillous, membranous part of the chorion.cho·ri·on (kō'rē-on), The outermost fetal membrance in human embryos, the villous part of which becomes the fetal part of the placenta. Synonym(s): membrana serosa (1) [G. chorion, membrane enclosing the fetus] chorion (kôr′ē-ŏn′)n. The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta.
cho′ri·on′ic (-ŏn′ĭk) adj.cho·ri·on (kōr'ē-on) The multilayered, outermost fetal membrane consisting of extraembryonic somatic mesoderm, trophoblast, and, on the maternal surface, its villi are bathed by maternal blood; as pregnancy progresses, part of the villous chorion becomes the fetal part of placenta.
Synonym(s): membrana serosa (1) . [G. chorion, membrane enclosing the fetus]chorion The outer of the two membranes that enclose the embryo. The inner is called the amnion.chorion - the superficial outer coat of the insect egg which is noncellular and secreted by the ovary around the ovum.
- an embryonic membrane of AMNIOTES formed from an outer ectodermal layer (see ECTODERM and an inner mesodermal layer (see MESODERM). see AMNION. In birds and mammals it forms the outer membrane covering the amniotic cavity, and in mammals the mesodermal component of the chorion fuses with the allantois to form the chorioallantoic PLACENTA. Here the chorion develops finger-like outgrowths, the chorionic villi, which project into blood spaces in the uterus of the mother. see CHORIONIC BIOPSY.
ChorionThe outermost membrane of the sac enclosing the fetus.Mentioned in: Prenatal Surgerychorion
Related to chorion: chorion laeve, chorion frondosumWords related to chorionnoun the outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals)Related Words- amniote
- chorionic villus
- mammal
- mammalian
- fetal membrane
- sac
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