Primitive streak

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(Anat.) an opaque and thickened band where the mesoblast first appears in the vertebrate blastoderm.

See also: Primitive

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The brutal crimes visited on Angelique Charlotte Bulatao show a primitive streak bubbling out of the muck and bursting through the surface calm.
That particular time point was supposedly adopted because in the next stage of development, the embryo forms the primitive streak, the first sign of a rudimentary nervous system, and is also supposedly past the point at which twinning can occur.
A prominent example of this coordination is found in the gastrulation of amniotes, where Brachyury (Bra), a transcription factor, is synchronously and transiently expressed in a localized population, the Primitive Streak (PS).
5) It is thought that this OEIS complex results from a single defect of early blastogenesis or defect of a caudal mesodermal migration during primitive streak period that later contributes to the formation of infra umblical mesenchyme, cloacal septum and vertebrae.
According to Jubb and Kennedy (1970) and Noden and Dalhunta (1985) conjoined twins are non-inherited teratological defects and monozygotic, thus monstrosities arise due to incomplete embryonic division into components usually at primitive streak development stage.
The majority of congenital defects are due to multifactorial etiology such as genetic or environmental (infectious diseases viruses drugs poisonings plants mineral salts and vitamin (A D E) deficiency) which cause the improper separation of primitive streak after day 13 of fertilization (El Sheikh et al.
They then used time-lapse microscopy to follow the cells in what has long been called "polonaise movements," the large-scale travels of ectoderm cells which lead to the formation of mesoderm along the midline where the primitive streak forms.
I consider the argument, thought to clinch the moral case for use of a human embryo solely as a means, that (i) only a human individual can be a person, (ii) because it can happen at any time before formation of the primitive streak that an embryo splits into monozygotic twins, no embryo in which the primitive streak has not formed is a human individual, and therefore (iii) no embryo in which the primitive streak has not formed is a person.
Unfortunately, they do not appear to take into account the fact that individuation is not assured biologically until the formation of the primitive streak around the fourteenth day after conception.
Last year Irish apprentice Sean Cleary died after suffering severe head injuries in a fall at Galway and Caroline Pratt, 42, was killed just two weeks ago when her horse, Primitive Streak, fell on her in the Burghley Horse Trials.