What is "chorion"

Chorion \Cho"ri*on\, n. [NL., fr. Gr. ?.]

1. (Anat.)

   1. The outer membrane which invests the fetus in the womb; also, the similar membrane investing many ova at certain stages of development.

   2. The true skin, or cutis.

2. (Bot.) The outer membrane of seeds of plants. [1913 Webster] ||

"outer membrane of the fetus," 1540s, medical Latin, from Greek khorion "membrane enclosing the fetus, afterbirth," perhaps from PIE *ghere- "gut, entrail" (see yarn).

n. 1 (context anatomy biology English) The protective and nutritive membrane in higher vertebrates that attaches the fetus to the uterus. 2 (context biology entomology English) The outer case of an insect egg. 3 (context botany English) The outer membrane of seeds of plants.

n. outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals)

In humans and most mammals, the chorion is one of the membranes that exist during pregnancy between the developing fetus and mother (the fetal membranes). The chorion and the amnion together form the amniotic sac.

It is formed by extraembryonic mesoderm and the two layers of trophoblast that surround the embryo and other membranes. The chorionic villi emerge from the chorion, invade the endometrium, and allow transfer of nutrients from maternal blood to fetal blood.

Chorion Limited was an international media production company with offices in London, New York and Sydney. The company produced TV shows and feature films, and was best known for its portfolio of entertainment brands. These included children's characters such as Paddington Bear, Peter Rabbit, The Mr. Men, The Very Hungry Caterpillar, Olivia, and Gaspard and Lisa. The company also owned the rights to the Agatha Christie Estate (including the Miss Marple and Poirot characters), Raymond Chandler, and Georges Simenon.

The company existed initially as a diversified entertainment company, with a portfolio of Intellectual Property rights, live entertainment venues and commercial real estate. From 2002 onwards, the business was refocused towards heritage IP Rights management and media production. Following a management buyout in 2006, Chorion delivered one new children's TV show every year and launched an associated merchandise range at retail.

The chorion is the outermost membrane around the embryo in mammals, birds and reptiles. It develops from an outer fold on the surface of the yolk sac, which lies outside the vitteline envelope and is developed by the follicle cells while the egg is in the ovary.