10371 IUPAC Gold Book - amniotic sac 10.1351/goldbook.10371 10371 current 1 Membranous structure in amniotes, within which the embryo and fetus develop. 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. 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 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) https://goldbook.iupac.org/terms/view/10371/html https://goldbook.iupac.org/terms/view/10371/json https://goldbook.iupac.org/terms/view/10371/plain 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 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. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-05-14T20:12:21+00:00