Plural of chorion, the outermost membrane that surrounds a developing embryo and helps form the placenta.
From Greek 'chorion' meaning 'membrane' or 'skin,' ultimately from Indo-European roots relating to enclosure or covering. The term entered English medical vocabulary in the 1600s as anatomists studied fetal development.
The chorion is so important that without it, your body couldn't even recognize your developing baby as part of your immune system—it acts like a diplomatic ambassador between mother and fetus!
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