notochord

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notochord

notochord , in biology, supporting rod running most of the length of animals of the phylum Chordata and present at varying times in the life cycle. Composed of large cells packed within a firm connective tissue sheath, the notochord lies between the neural tube (spinal cord) and the gut. The division of the phylum Chordata into subphyla is based on the structure of the notochord and the time of life in which it is present: In the subphylum Urochordata (tunicates) the notochord characterizes the larval, swimming, stage of the animals and does not extend into the head; in the subphylum Cephalochordata (lancelets) the notochord extends to the extreme tip of the head in both young and adults; and in the subphylum Vertebrata the notochord becomes surrounded by skeletal vertebrae during embryonic development—in higher vertebrates it is present in the early embryo only and is later completely replaced by the vertebrae.

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notochord

World Encyclopedia | 2005 | © World Encyclopedia 2005, originally published by Oxford University Press 2005. (Hide copyright information) Copyright

notochord In chordates, such as acorn worms, and the early embryonic stages of vertebrates, the flexible, primitive backbone; in mature vertebrates it is replaced by the spine.

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A Dictionary of Zoology | 1999 | | © A Dictionary of Zoology 1999, originally published by Oxford University Press 1999. (Hide copyright information) Copyright

notochord (chorda dorsalis) A some what flexible, rod-like structure, composed of disc-like, turgid cells, which extends virtually the entire length of the body of adult and/or larval members of the phylum Chordata. Lying below the nerve cord, but dorsal to the intestine, the notochord provides a form of flexible support to the body. In vertebrates the notochord is replaced wholly or partly by the vertebral column, but it is retained throughout life in Cephalochordata and Agnatha.

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	Continued growth and cell proliferation into adulthood in the notochord of the appendicularian Oikopleura dioica.(Author abstract) Magazine article from: The Biological Bulletin; 2/1/2008; ; 700+ words ; ...region and a motile tail containing a notochord and a dorsal nerve cord (Katz, 1983...loss of tail structures, including the notochord. The salps and doliolids (Thaliacea...undergo a metamorphosis through which the notochord (if initially formed at all) is lost...
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	A Novel Murine Gene, Sickle tail, Linked to the Danforth's short tail Locus, Is Required for Normal Development of the Intervertebral Disc Magazine article from: Genetics; 1/1/2006; ; 700+ words ; ...of a reporter gene was detected in the notochord during embryogenesis and in the nucleus...the third intron of the Skt gene. THE notochord is an integral component of the axial...CHIANG et eZ.1996). In addition, the notochord has major roles in vertebral column formation...
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	Research conducted at University of California has provided new information about life sciences. Newspaper article from: Science Letter; 2/10/2009; 700+ words ; ...simple chordate Ciona intestinalis, the notochord plate consists of just 40 cells, which...in the developing nerve cord directs notochord intercalation through non-MAPK signaling...polarized actin-rich protrusions in notochord cells, resulting in defective notochord...