chorion

chorion
—chorionic, chorial, adj.
/kawr"ee on', kohr"-/, n.
1. Embryol. the outermost of the extraembryonic membranes of land vertebrates, contributing to the formation of the placenta in the placental mammals.
2. Zool. the membrane around the eggs of certain insects, secreted by cells of the ovary.
[1535-45; < NL < Gk chórion membrane enclosing the fetus]

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also called  Serosa,  

      in reptiles, birds, and mammals, the outermost membrane around the embryo. It develops from an outer fold on the surface of the yolk sac. In insects the chorion is the outer shell of the insect egg.

      In vertebrates, the chorion is covered with ectoderm lined with mesoderm (both are germ layers) and is separated from other embryonic membranes by an extraembryonic body cavity, the coelom. In reptiles and birds it fuses with the allantois. In direct contact with the eggshell of reptiles and birds, this chorioallantoic membrane absorbs oxygen through the porous shell from the atmosphere for nourishment of the embryo; it also discharges waste carbon dioxide through the shell.

      In mammals (except marsupials), the chorion develops a rich supply of blood vessels and forms an intimate association with the endometrium (lining) of the female's uterus. Chorion and endometrium together form the placenta, which is the embryo's principal organ of respiration, nutrition, and excretion.

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Universalium. 2010.

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Look at other dictionaries:

  • chorion — [ kɔrjɔ̃ ] n. m. • 1541; gr. khorion 1 ♦ Biol. Membrane extérieure de l embryon des mammifères qui assure un contact intime avec la muqueuse utérine et joue un rôle dans la nutrition de l embryon. 2 ♦ Histol. Couche superficielle, hérissée de… …   Encyclopédie Universelle

  • Chorĭon [2] — Chorĭon (gr.), 1) Feld, Grundstück; daher Chorin dike, Klage, wegen Wegnahme od. widerrechtlicher Benutzung eines Feldes; 2) Bergfeste, Castell; so Chorion Kainon, Bergfeste im Innern von Pontos, wohin Mithridates seine Schätze flüchtete;… …   Pierer's Universal-Lexikon

  • chorion — [kôr′ē än΄] n. [ModL < Gr chorion, fetal membrane: for IE base see YARN] 1. the outermost of the two membranes that completely envelop a fetus 2. the outer membrane or shell of the eggs of insects and other invertebrates chorionic [kôr′ēän′ik] …   English World dictionary

  • Chorion — Cho ri*on, n. [NL., fr. Gr. ?.] 1. (Anat.) (a) The outer membrane which invests the fetus in the womb; also, the similar membrane investing many ova at certain stages of development. (b) The true skin, or cutis. [1913 Webster] 2. (Bot.) The outer …   The Collaborative International Dictionary of English

  • chorion — chorion. См. хорион. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Chorĭon [1] — Chorĭon (gr., lat. Corium, Anat.), 1) eigentlich Haut, Leder, Lederhaut, s. Haut; 2) Ei od. Schalenhaut, äußerste Begrenzung des Eies, Anfangs rund, durchsichtig glatt (Ch. laeve, Ch. pellucĭdum); mit Vergrößerung des Eichens wird das Ch. zottig… …   Pierer's Universal-Lexikon

  • Chorĭon — (griech., lat. corium), Haut, Leder, die äußere Eischale, bei den höhern Wirbeltieren die äußerste Hülle des Embryos. S. Allantois und Ei …   Meyers Großes Konversations-Lexikon

  • Chorion — Chorĭon (grch.; lat. Corĭum), Lederhaut, mittlere Eihaut des Embryos …   Kleines Konversations-Lexikon

  • Chorion — Chorion, Haut, die Hülle der Leibesfrucht mit Ausschluß der innersten der Schafhaut (vergl. Amnion, Embryo, Fötus) …   Herders Conversations-Lexikon

  • Chorion — Chorion, 1) von Follikelzellen gebildete sekundäre Eihülle des Insekteneies; 2) vom Trophoblasten gebildetes embryonales Ernährungsorgan der Placentatiere, das der Gebärmutterschleimhaut anliegt, Ausstülpungen (Zotten) bildet, mit diesen in die… …   Deutsch wörterbuch der biologie

  • chorion — CHORION. s. m. Terme d Anatomie. Nom d une des membranes du foetus …   Dictionnaire de l'Académie Française 1798

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