CHORION - Definition

Pronunciation:		'kowree`ân
WordNet Dictionary

	Definition:	[n] outermost membranous sac enclosing the embryo in higher vertebrates (reptiles; birds; mammals)

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	See Also:	chorionic villus, fetal membrane, sac

Webster's 1913 Dictionary

	Definition:	\Cho"ri*on\, n. [NL., fr. Gr. ?.] 1. (Anat.) (a) The outer membrane which invests the fetus in the womb; also, the similar membrane investing many ova at certain stages of development. (b) The true skin, or cutis. 2. (Bot.) The outer membrane of seeds of plants.

Biology Dictionary

	Definition:	The chorion is the outermost membrane enclosing the fetus. It is formed from tissues on the outside of the embryo such as the trophoblast, and the part of it attached to the uterus wall eventually develops into the placenta.

Glossary

	Definition:	a membrane derived from the amnion that lies just beneath the shell in the amniote egg and acts as a surface for oxygen absorption.