1A membranous sac containing yolk attached to the embryos of reptiles and birds and the larvae of some fishes.
〔动〕卵黄囊
Example sentencesExamples
Likewise, the occasional yolk sac tumor arising in liver has been reported in childhood.
The eggs take about 20 weeks to hatch and the now free-swimming ray is still reliant upon its yolk sac for a few more weeks before it begins to feed upon shrimps.
As young, begin to feed on attached yolk sacs, then plankton.
Unlike salmon, cod fry have no yolk sac on which to survive.
The neoplasm metastasized as the yolk sac component.
1.1A sac lacking yolk in the early embryo of a mammal.
（哺乳动物早期胚胎中的无卵黄）卵黄囊
Definition of yolk sac in US English:
yolk sac
noun
Zoology
1A membranous sac containing yolk attached to the embryos of reptiles and birds and the larvae of some fishes.
〔动〕卵黄囊
Example sentencesExamples
The eggs take about 20 weeks to hatch and the now free-swimming ray is still reliant upon its yolk sac for a few more weeks before it begins to feed upon shrimps.
Likewise, the occasional yolk sac tumor arising in liver has been reported in childhood.
Unlike salmon, cod fry have no yolk sac on which to survive.
The neoplasm metastasized as the yolk sac component.
As young, begin to feed on attached yolk sacs, then plankton.
1.1A sac lacking yolk in the early embryo of a mammal.