Exam 4 Review:  Chapter 12:  Spinal Nerves

spinal segment - The structural subdivisions of the spinal cord defined by the origin of a pair of spinal nerves from each subdividion or level within the cord (spinal segment); each subdivision is roughly equivalent to the individual vertebrae of the spinal/vertebral column (cervical, thoracic, lumbar and saccral), but in the adult are located somewhat superior to the comparable bone.

spinal nerves - The 31 pairs of mixed (m/s) nerves which arise from the various spinal segments of the spinal cord, which originate as dorsal and ventral roots which combine the in the region of the intervertebral foramen and shortly thereafter branch into various rami to innervate various regions of the body.

posterior root = dorsal root = sensory root - The collection of afferent sensory processes, emanating from the soma/cell bodies of the somatic and visceral sensory (afferent) neurons which reside in the posterior/dorsal/sensory root ganglion, which merge with the anterior root/ventral/motor root to form the spinal nerve laterally and which emerge from the posterior/dorsal horn at a particular spinal segment.

posterior / dorsal / sensory root ganglion - The enlargement found on each posterior/dorsal/sensory root which houses the soma/cell bodies of the somatic and visceral (afferent) sensory neurons serving a particular spinal segment.

anterior root = ventral root = motor root - The collection of efferent motor processes, emanating from the soma/cell bodies of the somatic and autonomic/visceral motor (efferent) neurons which reside in the lateral and anterior/ventral horns of the gray matter, which merge with the posterior root/dorsal/sensory root to form the spinal nerve laterally and which emerge from the anterior/ventral horn at a particular spinal segment.

ramus / rami - A general anatomical term for a branch which may be applied to a nerve, a blood vessel, or a region of a bone; in the peripheral nervous system, especially the first branches from each spinal nerve.

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