Dorsal and ventral roots from the spinal cord join near the inter-vertebral foramen where the dorsal root ganglia are found and the nerve branches form the typical nerve plan for trunk musculature.

Dorsal and ventral roots from the spinal cord join near the inter-vertebral foramen where the dorsal root ganglia are found and the nerve branches form the typical nerve plan for trunk musculature.
Dermatome overlap provides dual sensory innervation by the two adjacent segments. Testing of dermatomes requires considerations of this double overlap. Thus, three spinal nerves contribute to one dermatome in a way that loss of one spinal nerve does not produce an anesthetic zone.

Dermatome overlap provides dual sensory innervation by the two adjacent segments. Testing of dermatomes requires considerations of this double overlap. Thus, three spinal nerves contribute to one dermatome in a way that loss of one spinal nerve does not produce an anesthetic zone.