| 单词 | yolk sac |
| 释义 | > as lemmasyolk sac yolk sac n. a membranous sac attached to the developing embryo which acts as a source of nutrition. In egg-laying vertebrates the yolk sac encloses the egg yolk (sense 1a), while in placental mammals (including humans) the yolk sac is filled with vitelline fluid. ΘΚΠ the world > life > biology > biological processes > procreation or reproduction > reproductive substances or cells > [noun] > ovum or ootid > yolk > sac yolk sac1831 vitelline membrane1845 vitellicle1852 vitelline sac1880 1831 Edinb. New Philos. Jrnl. 10 111 Sketch showing the relative position, size, &c. of the allantois and yolk-sac, &c. in the fœtus of the sheep about three weeks old. 1971 Amer. Midland Naturalist 86 248 Glycogen stores were not appreciably reduced in heart, muscle or liver tissues during the 1st 31 days of fasting, while the yolk sac was completely consumed. 2014 A. Roberts Incredible Unlikeliness of Being 18 The fact that, as a tiny embryo, you had a yolk sac, even a small, un-yolky one, reveals something about your ancestry and the links between embryology and evolution. < as lemmas |
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