The outermost membrane surrounding an embryo of a reptile, bird, or mammal. In mammals (including humans), it contributes to the formation of the placenta.
- In insects, the genes that encode the proteins of the egg membrane, the chorion, become amplified in the surrounding follicle cells.
- A needle was used to roll the embryo out of the chorion.
- Care was exercised not to separate the amniotic sac into its components, the chorion and amnion.
- Example sentences
- Amniotic fluid, chorionic villi, or fetal serum can be tested for evidence of West Nile virus infection.
- Triple screening should not replace amniocentesis or chorionic villous sampling in pregnancies at high risk for trisomy 21.
- These authors found ultrastructural evidence of altered endothelial and smooth muscle cells within chorionic vessels exhibiting HEV-like lesions.
Mid 16th century: from Greek khorion.
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