chorion noun. ['kɔ:rɪǝn] M16.
[Greek khorion.]
1. Anatomy. The outermost membrane enveloping the foetus in mammals, birds, and reptiles. M16.
2. Entomology. The outer covering or shell of an insect's egg. M19.

Comb.:
chorionepithelioma, pl. -mas, -mata [-mǝtǝ], Medicine a carcinoma of maternal tissue, originating in the chorion.

■ chori'onic adjective of or pertaining to the chorion;

■ chorionic gonadotrophin, a hormone secreted during pregnancy by the placenta which stimulates continued production of progesterone by the ovaries;

■ chorionic villus sampling, a procedure for obtaining information about a foetus in which a sample of tissue is taken from the villi of the chorion (abbreviation

■ CVS): L19.

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