part of part of dorsal_to ventral_to develops_from existence starts during embryo stage multi-tissue structure neural tube digestive tract notochord (...) at some stage of its development, every chordate exhibits five uniquely derived characters or synapomorphies of the group: (...) (3) a stiff, longitudinal rod of turgid cells along the dorsal part of the body that is called a notochord (...).[well established][VHOG] A flexible rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes the nucleus pulposus of the intervertebral disc. The notochord is found ventral to the neural tube. AAO:0000327 Avascular multi-tissue structure composed of large vacuolated epithelial cells (chordablasts) and perichordal fibrous tissue.[VSAO] BTO:0001768 CALOHA:TS-0690 EHDAA2:0001277 EHDAA:1241 EHDAA:6021 EMAPA:16191 EV:0100002 FMA:85521 GAID:1311 In between vertebra the notochord becomes the nucleus pulposus, under it degenerates, and at anterior end in some species its tissue merges with some of the cranial bones.. Some organisms retain a post-embryonic notochord. MAT:0000281 MESH:A16.254.610 Rod-like principal supportive element of the embryo and larva, present in the midline just ventral to the neural tube, and differentiating during the segmentation period to form large vacuolated epithelial cells and a surrounding a sheath of fibrous and elastic layers. Layering of the sheath may differ in structure, thickness and development among groups; in cypriniforms there are actually three very thin layers to the sheath. A functional, well developed notochord is present throughout life in certain basal fish groups but not in cypriniforms. Kimmel et al, 1995.[TAO] Slender rod of fibrous connective tissue surrounding a core of fluid-filled cells of mesodermal origin; it lies above the gut and directly beneath the spinal cord. The notochord is present during early development and in a few cases it is retained through life; however, usually the notochord is replaced by the vertebral column.[AAO] TAO:0000135 The notochord appears early in embryogeny and plays an important role in promoting or organizing the embryonic development of nearby structures. In most adult chordates the notochord disappears or becomes highly modified. In some non-vertebrate chordates and fishes the notochord persists as a laterally flexible but incompressible skeletal rod that prevents telescopic collapse of the body during swimming[TOLWEB] UBERON:0002328 UMLS:C0028439 VHOG:0000199 VSAO:0000032 XAO:0000055 ZFA:0000135 embryonic notocord notochorda notochordal notocord relationship type change: differentiates_from mesoderm (AAO:0000304) CHANGED TO: develops_from mesoderm (UBERON:0000926)[AAO] uberon mesoderm-derived structure ectoderm-derived structure chordamesoderm notochordal plate axial skeletal system