yolk sac
| 1. |
(noun) membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes; circulates nutrients to the developing embryo |
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Related Words: sac |
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| 2. |
(noun) membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional |
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Related Words: sac |
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