notochord

(noun)

a flexible rodlike structure that forms the main support of the body in the lowest chordates; a primitive spine

Related Terms

  • nerve cord
  • chordate
  • pharyngeal slit
  • anencephaly
  • dorsal nerve cord
  • Wnt signaling pathway
  • ventral
  • neural tube
  • dorsal
  • vertebral column
  • neurulation

Examples of notochord in the following topics:

  • Phylum Chordata

    • The phylum Chordata contains all animals that have a dorsal notochord at some stage of development; in most cases, this is the backbone.
    • A notochord, or a longitudinal, flexible rod between the digestive tube and the nerve cord .
    • A dorsal nerve cord which develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord.
    • For example, tunicate larvae have both a notochord and a nerve cord which are lost in adulthood .
    • All chordates possess a notochord, or a type of flexible support rod, at some point in their development.
  • Characteristics of Chordata

    • Animals in the phylum Chordata share four key features: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
    • In some chordates, the notochord acts as the primary axial support of the body throughout the animal's lifetime.
    • The notochord, however, is replaced by the vertebral column (spine) in most adult vertebrates.
    • In chordates, it is located dorsally (at the top of the animal) to the notochord.
    • In chordates, four common features appear at some point during development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
  • Chordates and the Evolution of Vertebrates

    • Adults only maintain pharyngeal slits and lack a notochord, a dorsal hollow nerve cord, and a post-anal tail.
    • Members of Cephalochordata possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage.
    • They do not have a true brain, but the notochord extends into the head, which gives the subphylum its name ( "cephalo" is Greek for head).
    • (c) In the adult stage, the notochord, nerve cord, and tail disappear.
    • Adult lancelets retain the four key features of chordates: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
  • Agnathans: Jawless Fishes

    • The skeleton of a hagfish is composed of cartilage, which includes a cartilaginous notochord that runs the length of the body.
    • This notochord provides support to the hagfish's body.
    • Unlike true vertebrates, hagfishes do not replace the notochord with a vertebral column during development.
    • Their notochord is surrounded by a cartilaginous structure called an arcualia, which may resemble an evolutionarily-early form of the vertebral column.
  • Characteristics of Vertebrates

    • However, the subphylum Vertebrata is distinguished from the phylum Chordata by the development of the notochord into a bony backbone.
    • In vertebrates, the notochord develops into the vertebral column or spine: a series of bony vertebrae each separated by mobile discs .
    • However, a few vertebrates have secondarily lost their vertebrae and, instead, retain the notochord into adulthood (e.g., the sturgeon fish).
    • In chordates, the central nervous system is based on a hollow nerve tube that runs dorsal to the notochord along the length of the animal.
    • All chordates are deuterostomes, possessing a notochord.
  • Vertebrate Axis Formation

    • They found that the transplanted embryo now had two notochords: one at the dorsal site from the original cells and another at the transplanted site.
    • This suggested that the dorsal cells were genetically programmed to form the notochord and define the dorsal-ventral axis.
  • Establishing Body Axes during Development

    • They found that the transplanted embryo now had two notochords: one at the dorsal site from the original cells and another at the transplanted site.
    • This suggested that the dorsal cells were genetically programmed to form the notochord and define the axis.
    • These cell types are specified by the secretion of Shh from the notochord (located ventrally to the neural tube), and later from the floor plate cells.
  • The Evolution of Craniata and Vertebrata

    • In adult vertebrates, the vertebral column replaces the embryonic notochord.
  • Gene Expression for Spatial Positioning

    • The mesoderm also forms a structure called the notochord, which is rod-shaped and forms the central axis of the animal body.
  • Organogenesis

    • The mesoderm also forms a structure called the notochord, which is rod-shaped and forms the central axis of the animal body.
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