Fig. 26. Diagram showing stage of allantoic development with commencing constriction of the yolk-sac
Diagram showing later stage of allantoic development with commencing constriction of the yolk-sac.
--Mark Hill (talk) 12:38, 25 April 2013 (EST)
- yolk sac - An extraembryonic membrane which is endoderm origin and covered with extraembryonic mesoderm. Yolk sac lies outside the embryo connected initially by a yolk stalk to the midgut with which it is continuous with. The endodermal lining is continuous with the endoderm of the gastrointestinal tract. The extra-embryonic mesoderm differentiates to form both blood and blood vessels of the vitelline system. In reptiles and birds, the yolk sac has a function associated with nutrition. In mammals the yolk sac acts as a source of primordial germ cells and blood cells. Note that in early development (week 2) a structure called the "primitive yolk sac" forms from hypoblast, this is an entirely different structure.
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Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.
Cite this page: Hill, M.A. (2019, January 19) Embryology Gray0026.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Gray0026.jpg
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
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