ANHB2212 Study Guide - Final Guide: White Matter, Ligament, Sacrum
3 Jun 2018
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Spinal Cord and Spinal Nerves
Typical Spinal Nerve:
• Development
o Neural crest cells → precursor to dorsal root ganglia in PNS
o When the hypomere migrates it takes along its nerve supply →
ventral rami
o Nerve supply of the epimere that remains in situ → dorsal rami
• Morphology
o A spinal nerve is formed where the dorsal and ventral roots
converge and exit through the intervertebral foramen
o Dorsal roots → cell bodies of sensory neurons
o Ventral roots → cell bodies of motor neurons
o Spinal nerve → axons of sensory and motor neurons
o Upon emerging form the intervertebral foramen the mixed spinal
nerve gives off 2 main branches → rami
▪ Dorsal ramus
• Remains in situ
• Supplies
o Skin in the region overlying the vertebral
column
o Intrinsic musculature of the back
▪ Ventral ramus
• Continues forward to body wall and limbs
• Supplies
o Remainder of the skin
o Musculature of the back
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o Segmentation occurs when nerves emerge through a specific
intervertebral foramen and supply specific parts of the body
▪ Can be simple → adjacent innervation → thoracic nerves
▪ Can be complex → sacral plexus → innervates multiple
organs in different places
• Sympathetic Trunk
o Typical spinal nerve also contains sympathetic nerve fibers
o These exit via the ventral roots at levels T1-L2/3 → branch and
grow to enter the sympathetic chain ganglion
o White ramus communicans → presynaptic fibers carried to
ganglion
o Grey ramus communicans → bring postsynaptic fibers back from
ganglion
o Paravertebral ganglia → found either side of vertebrae
Spinal Meninges:
• Specialized membranes that cover the spinal cord and spinal nerve roots
• Collectively the meninges provide
o Protection
o Deliver nutrients
o Physical stability
o Shock absorption
• 3 layers
o Pia mater
o Arachnoid
o Dura mater
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find more resources at oneclass.com
