Title: chorion
Long Title: IUPAC Gold Book - chorion
DOI: 10.1351/goldbook.10516
Status: current

Definition
In human embryology, the cellular, outermost extra-embryonicmembrane, composed of trophoblast lined with mesoderm.
Note: The chorion develops villi, becomes vascularized by allantoic vessels, and forms the fetal part of the placenta.

In mammalian embryology, the cellular, outer extra embryonic membrane, not necessarily developing villi.
In biology, the noncellular membrane covering eggs of various animals, e.g., fish and insects.


Related Terms
- eggs: https://goldbook.iupac.org/terms/view/10640
- embryology: https://goldbook.iupac.org/terms/view/10649
- fetal: https://goldbook.iupac.org/terms/view/10718
- membrane: https://goldbook.iupac.org/terms/view/11555
- mesoderm: https://goldbook.iupac.org/terms/view/10944
- trophoblast: https://goldbook.iupac.org/terms/view/11327

Source
- PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 735 (https://doi.org/10.1515/pac-2015-1202)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/10516/html
- json: https://goldbook.iupac.org/terms/view/10516/json
- xml: https://goldbook.iupac.org/terms/view/10516/xml

Citation: Citation: 'chorion' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.10516
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
Collection: If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .
Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-05-10T08:49:38+00:00