Look up: Yolk Sac

1. yolk sac
   [n] - membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional 2. [n] - membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes
   Found on http://www.webdictionary.co.uk/definitio
   
   
2. Yolk Sac
   One of the protective membranes surrounding the embryo
   Found on http://www.encyclo.co.uk/local/20415
   
   
3. Yolk sac
   Yolk sac: Not all yolk has to do with birds' eggs. Human embryos have a yolk sac, too. The human yolk sac is a membrane outside the embryo that is 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 the formation of blood...
   Found on http://www.medterms.com/script/main/art.
   
   
4. 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.
   Found on http://www.encyclo.co.uk/visitor-contrib
   
   
5. yolk sac
   <embryology, ornithology> 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. ... (18 Nov 1997) ...
   Found on http://www.mondofacto.com/facts/dictiona
   
   
6. yolk sac
   umbilical vesicle noun membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional
   Found on http://wordnetweb.princeton.edu/perl/web
   
   
7. yolk sac
   the extraembryonic membrane connected with the midgut; in vertebrates below true mammals, it contains a yolk mass.
   Found on http://www.encyclo.co.uk/local/21001
   
   
8. yolk sac
   (from the article `reproductive system, animal`) ...embryos hatch in an extremely undeveloped but self-sustaining state as few as eight hours after fertilization. The yolk mass is large in some ... ...may be enclosed in the formative cells of the embryo, the bulk of the yolk remains an uncleaved mass, overgrown and surrounded by the cel...
   Found on http://www.britannica.com/eb/a-z/y/9
   
   
9. yolk sac
   large sac containing nutrients which is present in embryos of reptiles and amphibians.
   Found on http://www.chameleoncrazy.com/terminolog
   
   
10. Yolk Sac
    The highly vascular umbilical vesicle that envelopes the nutritive yolk of a developing embryo. The yolk sac is attached to the embyro's midgut.
    Found on http://www.pregnology.com/AZ/Y/1
    
    
11. yolk sac
    Type: Term Definitions: 1. in vertebrates with telolecithal eggs, the highly vascular layer of splanchnopleure surrounding the yolk of an embryo; 2. in humans and other mammals, the sac of extraembryonic membrane that is located ventral to the embryonic disk and, after formation of the gut tube, is ...
    Found on http://www.medilexicon.com/medicaldictio
    
    
12. yolk sac
    Sac containing the yolk in the egg of most vertebrates. The term is also used for the membranous sac formed below the developing mammalian embryo and connected with the umbilical cord
    Found on http://www.talktalk.co.uk/reference/ency
    
    
13. Yolk sac
    The `yolk sac` is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals. It functions as the developmental circulatory system of the human embryo, before internal circulation begins. In humans: It is the...
    Found on http://en.wikipedia.org/wiki/Yolk_sac