a membranous sac attached to the developing embryo which acts as a source of nutrition.
| 单词 | θ18939 | 
| 释义 | the world > life > biology > biological processes > procreation or reproduction > reproductive substances or cells > 			[noun]		 > ovum or ootid > yolk > sac (4)		 yolk sac1831 a membranous sac attached to the developing embryo which acts as a source of nutrition. vitelline membrane1845 vitelline membrane, vitelline sac, the transparent membrane which surrounds the yolk of an egg; the yolk-sac; the investing membrane of the embryo. vitellicle1852 A vitelline sac; a yolk-sac. vitelline sac1880 vitelline membrane, vitelline sac, the transparent membrane which surrounds the yolk of an egg; the yolk-sac; the investing membrane of the embryo. | 
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