单词	primitive streak
释义	primitive streak noun : an elongated band of cells that forms along the axis of a developing fertilized egg early in gastrulation and that is considered a forerunner of the neural tube and nervous system Example Sentences Recent Examples on the Web Laws limiting embryo research to either 14 days or formation of a structure called the primitive streak exist in several countries, including the United Kingdom, Sweden, and South Korea. Kelly Servick, Science | AAAS, 26 May 2021 In that transition, the embryo forms a furrow called the primitive streak and folds inward on itself while cells mature into different lineages that will later give rise to all the organs and tissues of the body. Kelly Servick, Science | AAAS, 23 May 2018 Word History Etymology translation of German Primitivstreifen First Known Use 1833, in the meaning defined above Medical Definition primitive streak noun : an elongated band of cells that forms along the axis of an embryo early in gastrulation by the movement of lateral cells toward the axis and that develops a groove along its midline through which cells move to the interior of the embryo to form the mesoderm
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