Noun
English Wikipedia has an article on:yolk sacWikipedia
yolk sac (plural yolk sacs)
(anatomy) A membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals.
After that, the epiblast and the hypoblast establish contact with the extraembryonic mesoderm until they cover the yolk sac and amnion. Source: Internet
Most other bony fish undergo metamorphosis from embryo to larva ( fry ) and then to the juvenile stage during absorption of the yolk sac, because after that phase the individual needs to be able to feed for itself. Source: Internet
In another 20% of cases, there is visualization of a gestational sac containing a yolk sac and/or an embryo. Source: Internet
Hatchling hellbenders are 25–33 mm long, have a yolk sac as a source of energy for the first few months of life, and lack functional limbs. Source: Internet
The juvenile coelacanth's broad yolk sac hangs below the pelvic fins. Source: Internet
The splanchnic depends on a continuous layer that covers the yolk sac. Source: Internet