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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
First Known Use of PRIMITIVE STREAK
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