Ventral nerve roots
Series of only motor roots in the GVE and GSE respsctive to each spinal cord segment that go to the periphery
What is a nerve root a composite of?
What protion of the spinal cord do ventral nerve rootlets form off of?
Ventral lateral sulcus
Dorsal nerve roots
- Series of only sensory roots (respective to each spinal cord segment) that collects to form the sensory axons to the spinal cord
- collection of central axonal processes from the pseudounipolar neurons in the dorsal root ganglions (directly medial to the root)
Dorsal root ganglion
- Aka the spinal ganglion/ posterior root ganglion
- the "bump" directly medial to the dorsal nerve root
- where all spinal nerve sensory nerve bodies are found
Central Axon Processes
One branch of the pseudounipolar neurons found in the spinal ganglion (the other is peripheral)
Where do dorsal rootlets enter the spinal cord?
Dorsal lateral sulcus
- formed near the intervertebral foramen/ distal to spinal ganglion
- ventral/dorsal nerve roots join to form this (same vertebral level)
- has both motor and sensory fibers
# of nerve pairs per a division of the spinal cord
8 cervical – 12 thoracic – 5 lumbar – 5 sacral – 1 coccygeal
How are cervical spinal nerves named?
What vertebrae they pass superior to
How are thoracic and lumbar nerves named?
By what vertebrae they pass inferior to
How do the spinal nerves change the more inferior they exit along the spinal cord?
Lower spinal nerves are much longer and have to travel inferiorly before traveling obliquely so they exit at the correct vertebral level
Sacral spinal nerves
- Are found in the sacral canal (S1-S4)
- Each must branch into ventral and dorsal rami before exiting via the ventral/dorsal sacral foramina
Which nerves exit via the sacral hiatus?
S5 and Co1 (coccygeal)
Dorsal/ventral roots of L2 to Co that emerge from the conus medullaris
- Lateral division of the spinal nerve that extends to/from the target nerve ending
- Each contains both afferent and efferent fibers
Innervate skin, muscles, joints, of vertebral column/nearby structures
- Innervate all structures anterior to the vertebral column including: limb structures/embryological derivates
- Much larger than dorsal rami
- Area of skin innervate by a single spinal cord segment
- Sensory cell bodies are in dorsal root ganglia
Torso dermatome pattern
Banded with some overlap
High yield dermatomes
T4 – Nipples; T10 – umbilicus; C6 –pad of thumb;
C8 – pinky; S5 – anus
Dermatomes and herpers zoster
Shingles presents as a stripped pattern on the torso because virus lives in the nerve cell bodies with the spinal ganglia
Limb dermatome pattern
Does not match the peripheral nerve due to plexuses
General segmental muscle innervation rule
Most muscles are innervated via 2 or more spinal nerves and 1 spinal nerve may help to supply many muscles