primitive streak


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streak

 [strēk]
a line, stria, or stripe.
angioid s's red to black irregular bands in the ocular fundus running outward from the optic disk.
primitive streak a faint white trace at the caudal end of the embryonic disk, formed by movement of cells at the onset of mesoderm formation, providing the first evidence of the embryonic axis. It eventually undergoes degenerative changes and disappears.

prim·i·tive streak

ridge of epiblast in the midline at the caudal end of the embryonic disc from which arises the intraembryonic mesoderm and definitive endoderm; achieved by inward and then lateral migration of cells; in human embryos, it appears on day 15 and provides visual evidence of the cephalocaudal axis.

primitive streak

a dense area on the central posterior region of the embryonic disk. It is formed by the morphogenetic movement of a rapidly proliferating mass of cells that spreads between the ectoderm and endoderm, giving rise to the mesoderm layer. This seamlike elongation indicates the cephalocaudal axis along which the embryo develops, and it corresponds to the blastopore of lower animal groups. Also called primitive line.

prim·i·tive streak

(prim'i-tiv strēk)
An ectodermal ridge in the midline at the caudal end of the embryonic disc from which arises the intraembryonic mesoderm; achieved by inward and then lateral migration of cells; in human embryos, it appears on day 15 and gives a cephalocaudal axis to the developing embryo.

primitive streak

a line of cells in the centre of the embryonic disc of reptiles, birds and mammals that forms the future axis of the embryo.

prim·i·tive streak

(prim'i-tiv strēk)
An ectodermal ridge in the midline at the caudal end of the embryonic disc from which arises the intraembryonic mesoderm; achieved by inward and then lateral migration of cells.

primitive streak,

n a furrowed, rod-shaped thickening in the middle embryonic disc that appears during the early formation of neural tissues and the mesoderm.

primitive

first in point of time; existing in a simple or early form; showing little evolution.

primitive groove
longitudinal furrow in the primitive streak of the embryo.
primitive knot
primitive node
enlarged cranial end of the primitive streak.
primitive streak
the thickened median area of the epiblast which sets out the future longitudinal axis of the early embryo.

streak

a line or stripe.

angioid s's
red to black irregular bands in the ocular fundus running outward from the optic disk.
streak canal
the papillary duct, the canal between the exterior and the lactiferous sinus within the teat of a ruminant.
primitive streak
a faint white trace at the caudal end of the embryonic disk, formed by movement of cells at the onset of mesoderm formation, providing the first evidence of the embryonic axis.
References in periodicals archive ?
Two new additions to the Primitive Streak collection, exploring the science behind the development and function of the lungs, will be seen for the first time.
Primitive Streak seems to have lasted the test of time, because it's not just fashion.
Below, implantation dress by Helen Storey, below right INNOVATIVE DESIGN The Primitive Streak dress BARE BONES Spinal column dress by Helen Storey
For Helen, Primitive Streak was also a turning point, a way into a new career which she felt enthusiastic about.
Mental is all about the the things we couldn't go in to with Primitive Streak, because in those first 1,000 hours of life parts of the brain and the nervous system have developed but notenough to do it justice in that project.
But even after the primitive streak stage, the question of potentiality is very ambiguous.
More importantly, Nusse and his colleagues determined that Wnt-responsive cells in the embryoid bodies also spontaneously form a primitive streak, though they never truly gastrulate.
But the primitive streak is the first indication we have that they can develop the kind of asymmetry that is seen in embryos.
Research between the appearance of the primitive streak (day 14) and the beginning of neural tube closure (day 21) to increase understanding of why the neural plate sometimes fails to close.
The report says that the appearance of the primitive streak is an important dividing line.
That omission sets the stage for some further puzzlement, the other side of the line-drawing coin, so to speak: if the emergence of the primitive streak is such a decisive event, why then should it not be used to set a limit on abortion as well?
The authors believe that even this time limit seems unnecessary because technical factors currently prevent the in vitro embryo from developing a primitive streak.