primitive streak

noun

Definition of primitive streak

: 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

Recent Examples of primitive streak from the Web

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, "Elusive master organizer of human embryo growth seen for the first time," 23 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'primitive streak.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of primitive streak

1833

in the meaning defined above

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Medical Dictionary

primitive streak

noun

medical Definition of primitive streak

: 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