Birds

• Mammals)
• Outermost membranous sac enclosing the embryo in higher vertebrates (reptiles

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

Wiktionary Word definitions in Wiktionary
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 ...

Wikipedia Word definitions in Wikipedia
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 Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Chorion \Cho"ri*on\, n. [NL., fr. Gr. ?.] (Anat.) The outer membrane which invests the fetus in the womb; also, the similar membrane investing many ova at certain stages of development. The true skin, or cutis. (Bot.) The outer membrane of seeds of plants. ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"outer membrane of the fetus," 1540s, medical Latin, from Greek khorion "membrane enclosing the fetus, afterbirth," perhaps from PIE *ghere- "gut, entrail" (see yarn ).