chorion

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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

/cho·ri·on/ (kor´e-on)
1. in human embryology, the cellular, outermost extraembryonic membrane, composed of trophoblast lined with mesoderm; it develops villi, becomes vascularized by allantoic vessels, and forms the fetal part of the placenta.
2. in mammalian embryology, the cellular, outer extraembryonic membrane, not necessarily developing villi.
3. in biology, the noncellular membrane covering eggs of various animals; e.g., fish and insects.chorion´ic

chorion frondo´sum  the part of chorion bearing villi.
chorion lae´ve  the nonvillous, membranous part of the chorion.
shaggy chorion , villous chorion c. frondosum.

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.

chorion

[kôr′ē·on]
Etymology: Gk, chorion, skin
the outermost extraembryonic membrane composed of trophoblast lined with mesoderm. It develops villi about 2 weeks after fertilization and is vascularized by allantoic vessels 1 week later. It gives rise to the placenta and persists until birth as the outer of the two layers of membrane containing the amniotic fluid and the fetus. Compare amnion.See also amniotic sac.
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Chorion

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

  1. the superficial outer coat of the insect egg which is noncellular and secreted by the ovary around the ovum.
  2. 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.

Chorion

The outermost membrane of the sac enclosing the fetus.
Mentioned in: Prenatal Surgery

chorion

the outermost of the fetal membranes, composed of trophoblast lined with mesoderm; it develops villi, becomes vascularized by allantoic vessels, and forms the fetal part of the placenta.

chorion frondosum
the part of the chorion covered by villi.
chorion laeve
the nonvillous, membranous part of the chorion.