Definition of yolk sac in English:

yolk sac

noun

Zoology
  • 1A membranous sac containing yolk attached to the embryos of reptiles and birds and the larvae of some fishes.

    • ‘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.’
    • ‘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.’
    1. 1.1 A sac lacking yolk in the early embryo of a mammal.