embryonic yolk sac

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• yolk-sac placenta — noun : a structure in some sharks resembling a placenta, consisting of the vascular embryonic yolk sac wall intimately associated with the vascular maternal uterine or oviducal wall, and serving to nourish the embryo …   Useful english dictionary

• yolk sac — n. Zool. 1. a saclike vascular membrane containing yolk, an outgrowth from the ventral surface of very yolky vertebrate embryos, as those of fishes, birds, or reptiles, that supplies nourishment to the embryo 2. a homologous organ in most… …   English World dictionary

• Yolk sac — Infobox Embryology Name = Yolk sac Latin = GraySubject = 11 GrayPage = 54 Caption = Human embryo of 2.6 mm. Caption2 = Human embryo from thirty one to thirty four days System = CarnegieStage = 5b Days = 9 Precursor = endoderm GivesRiseTo =… …   Wikipedia

• Yolk sac — Not all yolk has to do with birds’ eggs. Human embryos have a yolk sac, a membrane outside the embryo but connected by a tube (the yolk stalk) though the umbilical opening to the embryo’s midgut. The yolk sac serves as an early site for …   Medical dictionary

• yolk sac — noun 1. membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional • Syn: ↑vitelline sac, ↑umbilical vesicle, ↑vesicula umbilicus • Hypernyms: ↑sac 2. membranous structure enclosing the… …   Useful english dictionary

• yolk sac — One of the set of extra embryonic membranes, growing out from the gut over the yolk surface, in birds formed from the splanchnopleure, an outer layer of splanchnic mesoderm and an inner layer of endoderm …   Dictionary of molecular biology

• Embryonic hemoglobin — is a protein transcribed by the HBE1 gene in embryonic cells. It is produced in the blood islands in the embryonic yolk sac during the mesoblastic stage (1st week of pregnancy till end of pregnancy). The protein is commonly referred to as… …   Wikipedia

• yolk stalk — yolk′ stalk n. dvl a tubular connection between the yolk sac and the embryonic gut in the developing embryo • Etymology: 1895–1900 …   From formal English to slang

• embryonic membrane — n. any of several living membranes enclosing or closely associated with the developing vertebrate embryo, as the allantois, amnion, yolk sac, etc. * * * …   Universalium

• embryonic membrane — n. any of several living membranes enclosing or closely associated with the developing vertebrate embryo, as the allantois, amnion, yolk sac, etc …   English World dictionary

• embryonic disc — embryonic disc, the part of the inner cell mass of the blastula from which the embryo develops. It is located between two cavities, the amniotic cavity and the yolk sac. It consists of three germ layers, the ectoderm, the mesoderm, and the… …   Useful english dictionary