The Spinal Cord
Honors Anatomy& Physiology
for copying
Spinal Cord
• w/spinal nerves
contain neural
circuits that
mediate some of
your most rapid
reactions to
environmental
changes
Protective Structures
• 2 types of CT coverings surround &
protect delicate nervous tissue
1. bony vertebrae
2. tough CT meninges, w/cushion of
CSF
Meninges
• 3 CT coverings that encircle spinal
cord & brain:
• Spinal meninges covers spinal cord
• Cranial meninges covers brain
Meninges Layers: Dura Mater
“tough mother”
most superficial layer
made of dense, irregular CT
continuous with cranial meninges
forms sac from foramen magnum 
S2
• layer of adipose tissue between dura
mater & wall of vertebral cavity
(epidural space)
•
•
•
•
•
Middle Meninges:
Arachnoid Mater
• “spider-like”
• deep to dura mater, superficial to
pia mater
• contiguous with cranial arachnoid
• between dura & arachnoid =
subdural space
Innermost Meninges:Pia mater
•
•
•
•
“delicate”
thin, transparent CT
adheres to spinal cord & brain
between arachnoid & pia =
subarachnoid space
Spinal Tap
• aka lumbar puncture
• long needle inserted into subarachnoid
space
• adults: between L3 –L4 or L4 – L5
(inferior to lowest portion of spinal
cord)
• purpose: withdraw CSF for
– diagnostic purposes
– insert antibiotics/contrast media for
myelography/ anesthetics/ chemotherapy
Spinal Cord
• cylindrical with flattening of its AP
diameter
• adults:extends from medulla
oblongata  L2 vertebra
• newborns: extends to L3 or L4
• elongation of spinal cord stops ~age
3-4 but growth of vertebral column
continues
Spinal Cord: External View
• 2 obvious enlargements noted:
– cervical enlargement
• C4 – T1
• serve upper limbs
– lumbar enlargement
• T9- T12
• serve lower limbs
Spinal Cord: External View
• conus medullaris: tapered conical
structure of spinal cord below lumbar
enlargement ending @ L1 – L2
• filum terminale: extension of pia mater
extends inferiorly & anchors cord to
coccyx
• cauda equinae: “horse tail” nerves that
arise from lumbar, sacral, & coccygeal
portions of spine
Spinal Nerves
• 31 pairs spinal nerves emerge thru
intervertebral foramen
• 8 pair cervical nerves: C1 – C8
• 12 pair thoracic nerves: T1 - T12
• 5 pair lumbar nerves: L1 – L5
• 5 pair sacral nerves: S1 – S5
• 1 pair coccygeal nerves: Co1
Spinal Nerves
• 2 bundles of axons, called roots,
connect each spinal nerve to
segment of spinal cord
Spinal Cord Roots
1. posterior (dorsal) root
– only sensory axons
– each has dorsal root ganglion
containing cell bodies of sensory
neurons
2. anterior (ventral) root
– only motor axons
Internal Anatomy of
Spinal Cord
• 2 grooves penetrate white matter &
divide it in right & left sides:
1. anterior median fissure
1. deeper, wider of the 2
2. posterior median sulcus
1. shallower, narrow furrow
Spinal Nerves
• & the nerves that branch off them
are part of PNS
• emerge from vertebral column thru
intervertebral foramina
Spinal Nerves
• typically has 2 connections to spinal
cord
1. dorsal root (sensory)
2. ventral root (motor)
• classified as “mixed”
Distribution of Spinal Nerves
Spinal Nerve Plexuses
• a network of nerves (or veins, or
lymphatic vessels)
Cervical Plexus
• supplies skin &
muscles of the
head, neck, &
superior portion of
shoulders, chest, &
diaphragm
• C1 – C 5
Brachial Plexus
• supplies the
shoulders & upper
limbs
Lumbar Plexus
• supplies
anterolateral abd
wall, external
genitals, part of
lower limb
Sacral Plexus
• supplies buttocks,
perineum, & lower
limbs
Dermatomes
• cutaneous area developed from one
embryonic spinal cord segment &
receiving most of its sensory
innervation from one spinal nerve
• knowing which spinal cord segments
supply each dermatome makes it
possible to locate damaged regions of
the spinal cord
Spinal Cord Injuries
• most due to trauma
– cervical, lower thoracic, upper lumbar
most common regions involved
• paralysis
– depends on location, extent of damage
– monoplegia: 1 limb
– paraplegia: both lower limbs
– hemiplegia: upper limb, trunk, lower
limb on 1 side of body
– quadriplegia: all 4 limbs & trunk
Extent Muscle Paralysis
• C1 – C3: no function neck down, requires
ventilator to breathe
• C4 – C5: diaphragm, allows breathing
• C6 – C7: some arm, chest, allows
breathing, moving wheelchair
• T1 – T3: intact arm function
• T4 – T9: control of trunk above umbilicus
• T10 – L1: most thigh muscles, walk
w/long leg braces
• L1 – L2: most leg muscles, walk w/short
leg braces
Shingles
• acute infection of PNS
• caused by herpes zoster (chicken pox)
• virus stays in posterior root ganglion
– becomes reactivated normally immune
system will prevent it from spreading
– reactivated virus can overcome
weakened immune system  leaves
ganglion  travels down sensory
neurons supplying skin
Medical Terminology
• meningitis: inflammation of
meminges due to infection, bacterial
(worse) or viral, vaccine protests
against some bacterial causes:
headache, N/V, fever, stiff neck
• neuralgia: pain along a sensory
nerve, trigeminal neuralgia
• neuritis: inflammation of 1 or
several nerves
• paresthesis: abnormal sensation