Title: amniotic sac
Long Title: IUPAC Gold Book - amniotic sac
DOI: 10.1351/goldbook.10371
Status: current

Definition
Membranous structure in amniotes, within which the embryo and fetus develop.

Note
It consists of a thin but tough, transparent pair of membranes, the amnion and chorion, that hold the developing embryo (and later fetus) until shortly before birth.

Related Terms
- Membranous: https://goldbook.iupac.org/terms/view/11555
- amnion: https://goldbook.iupac.org/terms/view/10368
- amniotes: https://goldbook.iupac.org/terms/view/10369
- birth: https://goldbook.iupac.org/terms/view/10458
- chorion: https://goldbook.iupac.org/terms/view/10516
- fetus: https://goldbook.iupac.org/terms/view/10718

Source
- PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 721 (https://doi.org/10.1515/pac-2015-1202)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/10371/html
- json: https://goldbook.iupac.org/terms/view/10371/json
- xml: https://goldbook.iupac.org/terms/view/10371/xml

Citation: Citation: 'amniotic sac' 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.10371
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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: 2026-05-14T20:14:27+00:00