chorion

American  

[kawr-ee-on, kohr-] / ˈkɔr iˌɒn, ˈkoʊr- /

noun

1. Embryology. the outermost of the extraembryonic membranes of land vertebrates, contributing to the formation of the placenta in the placental mammals.

2. Zoology. the membrane around the eggs of certain insects, secreted by cells of the ovary.

---

chorion British  

/ ˈkɔːrɪən /

noun

1. 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

---

chorion Scientific  

/ kôr′ē-ŏn′ /

1. The outer membrane that encloses the embryo of a reptile, bird, or mammal. In mammals, the chorion contributes to the development of the placenta.

---

Other Word Forms

• chorial adjective
• chorionic adjective
• subchorionic adjective

Etymology

Origin of chorion

1535–45; < New Latin < Greek chórion membrane enclosing the fetus

Example Sentences

The chorion facilitates exchange of oxygen and carbon dioxide between the embryo and the egg’s external environment.

From Textbooks • Jan. 1, 2015

The chorionic villi of the chorion extend into the endometrium to form the fetal portion of the placenta.

From Textbooks • Jun. 19, 2013

Some grow to form the extra-embryonic membranes needed to support and protect the growing embryo: the amnion, the yolk sac, the allantois, and the chorion.

From Textbooks • Jun. 19, 2013

Four embryonic membranes form to support the growing embryo: the amnion, the yolk sac, the allantois, and the chorion.

From Textbooks • Jun. 19, 2013

This latter portion, the veil that passes from the edge of the placenta, is formed of the two membranes we have mentioned, namely, the chorion and the amnion.

From The Prospective Mother, a Handbook for Women During Pregnancy by Slemons, J. Morris (Josiah Morris)