primitive streak (redirected from primitive streaks)

streak (strēk) a line, stria, or stripe.

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angioid streaks  red to black irregular bands in the ocular fundus running outward from the optic disk.

fatty streak  a small, flat, yellow-gray area, composed mainly of cholesterol, in an artery; possibly an early stage of atherosclerosis.

meningitic streak  tache cérébrale.

Moore's lightning streaks  vertical flashes of light sometimes seen on the peripheral side of the field of vision when the eyes are moved, a benign condition.

primitive streak  a faint white trace at the caudal end of the embryonic disc, formed by movement of cells at the onset of mesoderm formation and providing the first evidence of the embryonic axis.

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primitive streak

n.

An ectodermal ridge in the midline at the caudal end of the embryonic disk from which the intraembryonic mesoderm arises.

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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.

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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.

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primitive

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

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primitive groove

longitudinal furrow in the primitive streak of the embryo.

primitive knot

see hensen's node.

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.

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streak

a line or stripe.

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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.