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The fetal membranes are the four extraembryonic membranes, associated with the developing embryo, and fetus in humans and other mammals. They are the amnion, chorion, allantois, and yolk sac. [1] The amnion and the chorion are the chorioamniotic membranes that make up the amniotic sac which surrounds and protects the embryo. [2]
28 de jul. de 2020 · While the amnion is an avascular membrane in most mammals, the yolk sac, allantois and chorion are highly vascularised to maximise nutrient and gas exchange between mother and foetus.
28 de jul. de 2020 · Primary yolk sac formation coincides with the emergence of extraembryonic mesoderm after implantation. Extraembryonic mesoderm is an integral part of amnion, yolk sac, allantois and chorion (Box 1), with critical roles in vascularisation and nutrient transport.
Four embryonic membranes form to support the growing embryo: the amnion, the yolk sac, the allantois, and the chorion. The chorionic villi of the chorion extend into the endometrium to form the fetal portion of the placenta.
The amnion is the membrane around the fetus. Amniocentesis is the transabdominal aspiration of fluid from the amniotic sac (the innermost of the membranes enveloping the embryo in utero). The amnion's epithelial cells have microvilli which may play a role in fluid transfer.
The allantois, along with the amnion, chorion, and yolk sac (other extraembryonic membranes), identify humans and other mammals, birds, and reptiles as amniotes. These extraembryonic membranes that form the embryo have aided amniotes in the transition from aquatic to terrestrial environments. [2] Fish and amphibians are anamniotes, lacking the ...
31 de ago. de 2011 · Their success is linked to the evolutionary innovation of the amnion, chorion and allantois as additional fetal membranes forming the cleidoic egg. It enables the development of the embryo independent from aquatic environments and is the prerequisite for laying eggs on land.
