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...

outer side, the amniotic sac is connected to the yolk sac, the allantois, and via the umbilical cord, the placenta. The yolk sac, amnion, chorion, and allantois...

gestational sac is a portion of the conceptus consisting of a cavity between Heuser's membrane and the trophoblast. During formation of the primary yolk sac, some...

between two fluid-filled cavities at either end: the primitive yolk sac and the amniotic sac. The epiblast is adjacent to the trophoblast and made of columnar...

vitellointestinal duct, the yolk stalk, the omphaloenteric duct, or the omphalomesenteric duct, is a long narrow tube that joins the yolk sac to the midgut lumen...

yet capable of feeding themselves and carry a yolk sac which provides stored nutrition. Before the yolk sac completely disappears, the young fish must mature...

envelope. The inner cell mass will give rise to the pre-embryo, the amnion, yolk sac and allantois, while the fetal part of the placenta will form from the...

Among animals which produce eggs, the yolk (/ˈjoʊk/; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to...

handle liquid waste. The allantois, along with the amnion, chorion, and yolk sac (other extraembryonic membranes), identify humans and other mammals, birds...

the trophoblast. When small, the sac cannot be distinguished from the early normal pregnancy, as there may be a yolk sac, though a fetal pole is not seen...