notochord

notochord

[noh-tuh-kawrd]
noun Embryology.
a rodlike cord of cells that forms the chief axial supporting structure of the body of the lower chordates, as amphioxus and the cyclostomes, and of the embryos of the vertebrates.

Origin:
1840–50; noto- + chord

notochordal, adjective
subnotochordal, adjective
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Collins
World English Dictionary
notochord (ˈnəʊtəˌkɔːd)
 
n
a fibrous longitudinal rod in all embryo and some adult chordate animals, immediately above the gut, that supports the body. It is replaced in adult vertebrates by the vertebral column
 
noto'chordal
 
adj

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Medical Dictionary

notochord no·to·chord (nō'tə-kôrd')
n.

  1. A flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive backbone.

  2. A similar structure in embryos of higher vertebrates, from which the spinal column develops.


no'to·chord'al adj.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
notochord   (nō'tə-kôrd')  Pronunciation Key 
A flexible rodlike structure that forms the main support of the body in all chordates during some stage of their development. In vertebrates, the notochord develops into a true backbone in the embryonic phase. Primitive chordates, such as lancelets and tunicates, retain a notochord throughout their lives.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

notochord

flexible rodlike structure of mesodermal cells that is the principal longitudinal structural element of chordates and of the early embryo of vertebrates, in both of which it plays an organizational role in nervous system development. In later vertebrate development, it becomes part of the vertebral column. The notochord derives during gastrulation (infolding of the blastula, or early embryo) from cells that migrate anteriorly in the midline between the hypoblast and the epiblast (inner and outer layers of the blastula). These cells coalesce immediately beneath the developing central nervous system. With the formation of the vertebral column, the notochord is incorporated into the column as the centres of the intervertebral discs, called the nuclei pulposi, which cushion the vertebrae.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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