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The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though yolk sac is far more widely used. The yolk sac is one of the fetal membranes and is important in early embryonic blood ...
In the human embryo, the vitelline duct, also known as the vitellointestinal duct, [1] the yolk stalk, [1] the omphaloenteric duct, [1] or the omphalomesenteric duct, [1] is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus. [2]
The vitelline veins drain the yolk sac during early embryonic development. [ 1 ] [ 5 ] They also drain the gut tube in embryos once this has formed from the yolk sac. [ 2 ] [ 6 ]
Blood is conveyed to the wall of the sac by the vitelline arteries (a branch of the dorsal aorta), and after circulating through a wide-meshed capillary plexus, is returned by the vitelline veins to the tubular heart of the embryo. This constitutes the vitelline circulation, and by means of it nutritive material is absorbed from the yolk-sac ...
The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle . In humans, the yolk sac is important in early embryonic blood supply.
Like the veins, they play an important role in the vitelline circulation of blood to and from the yolk sac of a fetus. They are a branch of the dorsal aorta . They give rise to the celiac artery , superior mesenteric artery , and inferior mesenteric artery .
The allantois (/ ə ˈ l æ n t oʊ ɪ s / a-LAN-toe-iss; [1] pl.: allantoides or allantoises) is one the extraembryonic membranes arising from the yolk sac.It is a hollow sac-like structure filled with clear fluid that forms part of the developing conceptus in an amniote that helps the embryo exchange gases and handle liquid waste.
While the primary yolk sac is forming, extraembryonic mesoderm migrate into the blastocyst cavity and fill it with loosely packed cells. When the extraembryonic mesoderm is separated into two portions, a new gap arises called the gestational sac. This new cavity is responsible for detaching the embryo and, its amnion and yolk sac, from the far ...