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Spinal Cord
Spinal Nerves
Chapter 10
Spinal Cord
Part of the CNS
About 16-18 inches long
Extends from the foramen magnum to the
end of L1
Main pathway for information flow to and
from the brain
Gross Anatomy of the Spinal Cord
Cord is divided into 31 segments: cervical,
thoracic, lumbar and sacral
Cervical and lumbar diameter
enlargements
Covered by same membranes as the brain
At about L1 the cord divides into many
long ventral and dorsal roots called the
cauda equina (horses tail)
Internal structure
2 grooves divide spinal cord in ½ :
(anterior median fissure and posterior median
sulcus)
Spinal Cord White Matter
White matter is divided into columns
Columns contain TRACTS; composed of axons
of similar structure/function
All axons in a tract relay information in the same
direction
Specific tracts convey either sensory or motor
commands:
ASCENDING TRACTS relay sensory
information toward the brain
DESCENDING TRACTS relay motor information
into the spinal cord
Spinal Cord Gray Matter
Gray matter is organized into nuclei – neuron
cell bodies, dendrites, unmyelinated axons,
neuroglia
“Horns” (anterior, posterior, lateral):
Anterior: Motor nuclei send out commands to
peripheral effectors, skeletal muscles
Posterior: Sensory nuclei receive and relay
sensory information
Lateral: autonomic motor neurons (smooth
muscle, cardiac muscle, glands)
Nerve Distribution - sensory
Nerve Distribution - motor
Spinal Cord and Meninges
Spinal cord and meninges
(layers of connective tissue)
Outer= Dura mater (“tough mother”)
Middle= Arachnoid mater (“spider mother”)
Inner= Pia mater (“delicate mother”)
Ganglia and roots
Each spinal segment has a pair of dorsal root
ganglia (sensory neuron cell bodies).
Dorsal root enters cord; ventral root leaves cord
Dorsal root ganglia –
sensory neuron cell
bodies (bulge)
Ventral root – motor
output
Dorsal root – sensory
input
Spinal nerve - mixed
Spinal nerves
extend out through
the intervertebral
foramen.
After passing through the intervertebral foramen a
spinal nerve divides into several branches =
plexus (cervical, brachial, lumbar, sacral)
Cervical Plexus
Brachial plexus
Brachial plexus
Lumbar plexus and Sacral plexus
Epidural
Epidural analgesia
Pain medication
placed into the
epidural space
Often used to block
pain associated with
child birth
Continuous infusion
Blocks pain not
muscle activity
Some of the reasons your doctor
may want to do a spinal tap
include the following:
◦ To look for infection (bacteria)
◦ To check to see if there is
bleeding around the brain (small
amounts of blood will be found in
the fluid)
◦ To look for causes of
unexplained seizures
◦ To look for causes of headaches
◦ To evaluate for uncommon
diagnoses such as multiple
sclerosis, Lyme disease, GuillainBarré syndrome, and several
others.
◦ To administer certain types of
chemotherapeutics medications in
the treatment of some cancers
Spinal Tap:
removal of CSF
Spinal Cord Injuries
Two general types of injuries
Complete - no function below the affected
area of the cord
– C1 - C3 injury breathing affected - respirator
– C4 - C7 quadriplegia (arms and legs)
Incomplete - some function below the
affected area of the cord
– Thoracic area and below - paraplegia (legs)
Types of paralysis
Cause of Spinal Cord Injuries
Sudden traumatic blow to spine that
fractures or dislocates vertebrae
Bone fragments, disc material bruise or
tear the spinal cord tissue
Cord swells, blood supply cells can stop,
neurons die, cord is damaged beyond
repair
Treatment of Spinal Cord
Injuries
Minimize further injury
– Realign spine and immobilize (surgery)
– Steroid medication to reduce swelling
– Methylprednisolone in first 8 hours reduces
swelling, inflammation and nerve cell damage
Rehabilitation
Dealing with long term complications