The nervous system develops from the dorsal neural tube of the embryo, differentiating into a somatic division (associated with the somites — skin, skeletal muscle, and bone derived from paraxial mesoderm) and a visceral division (associated with internal structures such as the gut, blood vessels, glands, and cardiac muscle). Each division carries both sensory (afferent) and motor (efferent) fibers, following the organizing principle that sensory fibers enter the spinal cord dorsally while motor fibers exit ventrally. This is a foundational concept in neuroanatomy and embryology, describing how the peripheral nervous system's segmental wiring arises from and mirrors the segmental organization of the developing body.
The nervous system develops from the dorsal neural tube of the embryo, differentiating into a somatic division (associated with the somites — skin, skeletal muscle, and bone derived from paraxial mes…