chorion (redirected from chorions)

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.

---

cho·ri·on (kôr-n)

n.

The outer membrane enclosing the embryo in reptiles, birds, and mammals. In placental mammals it contributes to the development of the placenta.

---

chori·onic (-nk) adj.

---

Chorion

The outermost membrane of the sac enclosing the fetus.

Mentioned in: Prenatal Surgery

---

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.

---

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.