relationship type change: differentiates_from mesoderm (AAO:0000304) CHANGED TO: develops_from mesoderm (UBERON:0000926)[AAO]

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]

https://github.com/wdahdul, https://github.com/cmungall

http://upload.wikimedia.org/wikipedia/commons/6/64/Gray19_with_color.png

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.

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], Avascular multi-tissue structure composed of large vacuolated epithelial cells (chordablasts) and perichordal fibrous tissue.[VSAO]

uberon

notochorda

notochordal

(...) 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]

UBERON:0002328

• perichordal tissue
• elastica externa of notochord

• neural plate
• neural tube basal plate

• perichordal bone

• nucleus pulposus
• floor plate

• notochord posterior region
• perichordal tissue
• flexural organ
• vacuolated notochordal tissue
• elastica externa of notochord