Some hypaxial muscles also stay close to the vertebrae, but in contrast, many hypaxial muscles spread out grow around the viscera to form a muscular body wall . The hypaxial mesoderm gives rise to the limbs as well, but with several somites contributing, hence plexuses , e.g, brachial, that represent the nerve input. The dorsal and ventral roots that come out the brain are the cranial nerves , and the ones coming from the spinal cord, spinal nerves . The parasympathetic nervous system originates from cranial and caudal sources. Many nerve cell bodies are found in clusters called ganglia peripheral to the central nervous system, formed by migrating neural crest cells .
Every body segment contains sympathetic ganglia from which postganglionic axes can spread.
Sympathetic motor fibers running out of the ventral ramus aim for the pinkish grey lumps of paravertebral ganglia, which connected together form the sympathetic trunk . Formation of the vertebral body, the vertebral arch, and the transverse and spinous processes via parts of the somites. Failure of the vertebral arch to fuse results in spina bifida , especially seen in the lumbar region. The intervertebral discs support most of the weight of the vertebral column. To help limit the motion of these joints are anterior and posterior longitudinal ligaments of the spine, as well as interspinous , supraspinous ligaments and ligamenta flava .