extraembryonic membranes

the membranous structures that surround the embryo and contribute to the placenta and umbilical cord. They include the amnion, chorion, allantois, and yolk sac. In humans the allantois is always very small and by the end of pregnancy the amnion and chorion have fused into a single membrane and the yolk sac has disappeared.

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the trophoblastic parts of the conceptus that provide for the support of the embryo or fetus by attachment, mechanical protection, endocrine action, and the mediation of chemical exchange with the maternal circulation. They include the yolk sac (umbilical vesicle), allantois, amnion, umbilical cord, and chorion, including the placenta. Called also fetal m's.

Medical dictionary. 2011.

Look at other dictionaries:

  • extraembryonic membranes — the membranous structures that surround the embryo and contribute to the placenta and umbilical cord. They include the amnion, chorion, allantois, and yolk sac. In humans the allantois is always very small and by the end of pregnancy the amnion… …   The new mediacal dictionary

  • Оболочки Внезародышевые (Extraembryonic Membranes) — оболочки, окружающие эмбрион и участвующие в образовании плаценты и пуповины. К ним относятся: амнион, хорион, аллантоис и желточный мешок. У человека аллантоис очень маленький;к концу беременности амнион и хорион сливаются в одну оболочку, а… …   Медицинские термины

  • extraembryonic — Outside the embryonic body; e.g., those membranes involved with the embryo s protection and nutrition which are discarded at birth without being incorporated in its body. * * * ex·tra·em·bry·on·ic .em brē än ik adj situated outside the embryo… …   Medical dictionary

  • extraembryonic — adjective Date: 1901 situated outside the embryo; especially developed from the zygote but not part of the embryo < extraembryonic membranes > …   New Collegiate Dictionary

  • extraembryonic blastoderm — the region of the blastoderm forming membranes rather than the embryo proper …   Medical dictionary

  • extraembryonic membrane — ex′traembryon′ic mem′brane n. dvl any of the membranes derived from embryonic tissue that lie outside the embryo, as the allantois, amnion, chorion, and yolk sac …   From formal English to slang

  • fetal membranes — extraembryonic m s …   Medical dictionary

  • ОБОЛОЧКИ ВНЕЗАРОДЫШЕВЫЕ — (extraembryonic membranes) оболочки, окружающие эмбрион и участвующие в образовании плаценты и пуповины. К ним относятся: амнион, хорион, аллантоис и желточный мешок. У человека аллантоис очень маленький;к концу беременности амнион и хорион… …   Толковый словарь по медицине

  • Eggshell — The term eggshell is a term for the outer covering of a hard shelled egg, and some forms of eggs with soft outer coats.The generalized eggshell structure, which varies widely among species, is a protein matrix lined with mineral crystals, usually …   Wikipedia

  • Amnion — A thin membrane surrounding the fetus during pregnancy. The amnion is the inner of the two fetal membranes (the chorion is the outer one). It contains the amniotic fluid. * * * Innermost of the extraembryonic membranes enveloping the embryo in… …   Medical dictionary

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