Primitive Streak

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primitive streak

[′prim·əd·iv ′strēk]
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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Helen says: "Primitive Streak came at a time in my life when I had just stopped commercial fashion and I was looking for a new way to stretch myself while using the knowledge I had gained along the way as a fashion designer.
Hundreds of onlookers looked on in horror as Caroline, 42, a friend of Royal riders Princess Anne and daughter Zara, tumbled from her mount, Primitive Streak.
The result was Primitive Streak, a series of dresses designed to represent the first 3-D structures within the embryo that defines its head and tail axis, the line of the body.
that the human person does not begin at conception, but roughly two weeks later at segmentation (or the "primitive streak" stage) after which there is no longer any possibility of identical twinning.
He was seventh on Walter's Destiny in the Cadbury Business Park Handicap Hurdle and then Primitive Streak was third behind Far East in the Improve Your Handicap Chase.
[6,7] This theory discusses interference with the normal development of the growth center of the embryo (Stated to be the primitive streak in man) allowing the development of secondary growth center.
However, prior to the development of the primitive streak (the precursor of the nervous system), the embryo can become two or more people, making any identification between the early embryo and the later person impossible.
Jump jockey Guy Upton, aged 32, announced his retirement minutes before finishing third on Primitive Streak at Wincanton yesterday.
Among examples of acceptable research the panel noted the following: * Research on embryos left over from IVF or preimplantation diagnosis up to the appearance of the primitive streak (day 14) - and on embryos created in vitro when a "compelling" case can be made for the scientific and therapeutic value of the research.
Conjoined twinning arises when the twinning event occurs at about the primitive streak stage of development at about 13-14 days after fertilization (2,3), Conjoined twinning occurs by the incomplete splitting of the embryonic axis and, with the exception of parasitic conjoined twins, all are symmetrical and "the same parts are always united to the same parts".
The report says that the appearance of the primitive streak is an important dividing line.
The main ways that moral consideration appear to enter into research on the embryo are (1) to set a limit to the duration of the research (provisionally, the appearance of the primitive streak at fourteen days post-fertilization, or potentially, the closure of the neural tube some days later), and (2) to minimize the number of fertilized eggs required for research.