notochord
Primitive spinal rod
A notochord is a flexible rod of cells that runs along the back of an embryo, providing structural support.
In vertebrates, it appears early in development and is later replaced by the spinal column.
Some primitive animals like lancelets retain the notochord throughout life.
The notochord defines the phylum Chordata—all chordates possess one at some developmental stage.
Embryonic tissue forming muscles
- gastrulationEmbryo forms primary layers
- inductionFormal admission process
- morphogenesisDevelopmental shape emergence
- ectodermEmbryo's outer cell layer
endoderm · organogenesis · neural tube · dorsal · fate mapping · noggin
Spinal column animal
- lanceletPrimitive marine chordate
- tunicateCoated marine invertebrate
- craniateSkull-possessing animal
- sea squirtBarrel-shaped marine invertebrate
Along a rotation line
- flexibleAble to bend freely
- hydrostaticOf fluid pressure at rest
- sheathProtective blade covering
- collagenStructural body protein
stiffening · elastic · cylindrical · longitudinal · fibrous · segmented
Of one's forebears
- phylogenyEvolutionary relationships among organisms
- CambrianEarliest Paleozoic period
- fossilsPreserved ancient organism traces
- homologyStructural similarity through descent
common ancestor · paleontology · Burgess Shale · basal · primordial · bilateral symmetry · body plan · cladistics
Column of vertebrae
- vertebraeInterlocking bones of spine
- backboneVertebral column, or courage
- spinal columnSegmented skeletal axis
- remnantWhat stays after most goes
vestigial · herniated disc · cervical · lumbar · thoracic · sacral · ossification · vertebral body
mesoderm
Embryonic tissue forming muscles
- gastrulationEmbryo forms primary layers
- inductionFormal admission process
- morphogenesisDevelopmental shape emergence
ectoderm · endoderm · organogenesis · neural tube · dorsal · fate mapping · noggin
vertebrate
Spinal column animal
axial
Along a rotation line
- flexibleAble to bend freely
- hydrostaticOf fluid pressure at rest
- sheathProtective blade covering
collagen · stiffening · elastic · cylindrical · longitudinal · fibrous · segmented
ancestral
Of one's forebears
- phylogenyEvolutionary relationships among organisms
- CambrianEarliest Paleozoic period
- fossilsPreserved ancient organism traces
homology · common ancestor · paleontology · Burgess Shale · basal · primordial · bilateral symmetry · body plan · cladistics · divergence
spine
Column of vertebrae
- vertebraeInterlocking bones of spine
- backboneVertebral column, or courage
- spinal columnSegmented skeletal axis
remnant · vestigial · herniated disc · cervical · lumbar · thoracic · sacral · ossification · vertebral body · degenerative disc disease
notochordvertebral column
Segmented axial skeletal structure
spine · backbone · spinal column · vertebrae · exoskeleton