Notochord

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Notochord
Transverse section of a chick embryo of forty-five hours' incubation.
Details
Precursor	Axial mesoderm
Gives rise to	Nucleus pulposus
Identifiers
Latin	notochorda
MeSH	C000000
TE	E5.0.1.1.0.0.8
FMA	85521
Anatomical terminology [edit on Wikidata]

In zoology and developmental anatomy, the notochord is an elastic, rod-like anatomical structure found in many deuterostomal animals. A notochord is one of five synapomorphies, or characteristics used to define a species as a chordate.

The notochord is derived from the embryonic mesoderm and consists of an inner core of vacuolated cells filled with glycoproteins, covered by two helical collagen-elastin sheaths. It lies along the rostral-caudal axis of the body (i.e. longitudinally or "head to tail"), dorsal to the gut tube and ventral to the dorsal nerve cord. Some chordates, such as tunicates, develop notochord during the larval stage but lose it through subsequent stages into adulthood.

The notochord is important for signaling the dorso-ventral patterning of cells coming from the mesodermal progenitors. This helps form the precursors needed for certain organs and the embryo to develop. In summary, the notochord plays essential roles in embryonic development.

The notochord provides a directional reference to the surrounding tissue as a midline structure during the embryonic development, acts as a precursor for vertebrae and a primitive axial endoskeleton, and can allow for facilitated tail motion when swimming.^[1]