Editing Ontogeny (section)

===== Primary Neurulation =====
The diagram to the right illustrates primary neurulation, which is the process of cells surrounding the neural plate interacting with neural plate cells to proliferate, converge, and pinch off to form a hollow tube above the [[notochord]] and mesoderm.  This process is discontinuous and can start at different points along the cranial-caudal axis necessary for it to close.<ref name="Müller O'Rahilly Embryonic Development of the Central Nervous System"/>  After the neural crest closes, the neural crest cells and ectoderm cells separate and the ectoderm becomes the epidermis surrounding this complex.  The neural crest cells differentiate to become components of most of the peripheral nervous system in animals.  Next, the notochord degenerates to become only the [[Intervertebral disc|nucleus pulposus]] of the [[intervertebral disc]]s and the mesoderm cells differentiate to become the [[somite]]s and skeletal muscle later on.  Also during this stage, the neural crest cells become the spinal ganglions, which function as the brain in organisms like [[earthworm]]s and [[arthropod]]s.<ref>{{Cite web |title=ganglion {{!}} physiology {{!}} Britannica |url=https://www.britannica.com/science/ganglion |access-date=2022-04-09 |website=www.britannica.com |language=en}}</ref>  In more advanced organisms like [[amphibian]]s, [[bird]]s and [[mammal]]s;<ref name="Gilbert-2000" /> the spinal ganglions consists of a cluster of nerve bodies positioned along the spinal cord at the dorsal and ventral roots of a spinal nerve, which is a pair of nerves that correspond to a vertebra of the spine.<ref>{{Cite web |title=spinal nerve {{!}} Definition, Function, Diagram, Number, & Facts {{!}} Britannica |url=https://www.britannica.com/science/spinal-nerve |access-date=2022-04-09 |website=www.britannica.com |language=en}}</ref>