yolk sac


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. 2004.

Look at other dictionaries:

  • 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 — yolk′ sac n. dvl an extraembryonic membrane that encloses the yolk of eggs • Etymology: 1860–65 …   From formal English to slang

  • yolk sac — yolk sac. См. желточный мешок. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • 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 — 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 — 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 — thin membrane which surrounds the yolk of an egg and supplies nutrients to the embryo (in mammals, the yolk sac ceases to function when the placenta forms) …   English contemporary dictionary

  • yolk sac — noun Date: 1861 a membranous sac of most vertebrates that encloses the yolk, is attached in most forms (as in humans) through the yolk stalk with the intestinal cavity of the embryo, and is supplied with blood vessels that transport nutritive… …   New Collegiate Dictionary

  • yolk sac — a sac containing yolk used for nourishment in larval fish …   Dictionary of ichthyology

  • yolk sac — noun A membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals …   Wiktionary

  • yolk sac — noun Zoology a membranous sac containing yolk attached to the embryos of reptiles and birds and the larvae of some fishes …   English new terms dictionary


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