chorion

noun3

1. •
   The protective and nutritive membrane in higher vertebrates that attaches the fetus to the uterus.

   • The allantois fuses with the chorion, forming a small round area, the allentochorion. This region becomes the placenta (Fig. 3). — 2002
2. •
   The outer case of an insect egg.

   • The chorion has a predominantly lamellar structure, the lamellae being two-dimensional networks of protein fibrils. — 1994
3. •
   The outer membrane of seeds of plants.