| 释义 |
Primitive streak
| (Anat.) | an opaque and thickened band where the mesoblast first appears in the vertebrate blastoderm. |
See also: Primitive
Primitive Streak
primitive streak[′prim·əd·iv ′strēk] (embryology) A dense, opaque band of ectoderm in the bilaminar blastoderm associated with the morphogenetic movements and proliferation of the mesoderm and notochord; indicates the first trace of the vertebrate embryo. Primitive Streak a longitudinal thickening of the outer layer of the embryonic disk, or blastodisk, in the embryos of birds, mammals, and humans; it is formed during the process of gastrulation. Mesodermal cells migrate from the primitive streak to the area between the ectoderm and endoderm. These cells later form the somites and lateral plates. In the anterior end of the primitive streak, the cell accumulation known as Hensen’s node develops. This cellular material becomes the notochord. primitive streak
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 disk" >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 streakridge 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. Synonym(s): gastrulation streak, germinal streakprim·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. ThesaurusSeestreak |