Definition of primitive streak in English:

Share this entry

primitive streak


The faint streak that is the earliest trace of the embryo in the fertilized ovum of a higher vertebrate.
Example sentences
  • After fourteen days, there begins to appear the first traces of what will become the central nervous system of the embryo, the primitive streaks (or the two primitive streaks, since at about this time identical twins may be formed).
  • Some embryologists and ethicists insist that only after the primitive streak develops can this being be called an embryo.
  • Some have argued that because an embryo can split before the primitive streak appears and form the bases of identical twins, it does not merit the same protection as the embryo that is the basis for a definite individual person.

For editors and proofreaders

Syllabification: prim·i·tive streak

Share this entry

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.