Anatomy of the Spinal Cord
 Structure
of the spinal cord
 Tracts
of the spinal cord
 Spinal
cord syndromes
Spinal Cord
- Comparable to
Input-Output (IO) System of the Computer
- Spinal Nerve (C8, T12, L5, S5, Cx1)
- Segmental Structure of Neural Tube Origin
Spinal segment
C8, T12, L5, S5, Cx1
Anterior (Ventral) Root
Posterior (Dorsal) Root
Dorsal Root (Spinal) Ganglion
Root - Rootlets
Spinal Cord
External Figure
Conus Medullaris (L1-2)
Spinomedullary Junction
- Foramen Magnum, Pyramidal decussation, C1 ventral root
Enlargements
- cervical (C5-T1) & lumbosacral (L1-L4)
Longitudinal Fissures
- anterior median fissure
- anterolateral fissure
- posterior median sulcus
- posterolateral sulcus
Conus Medullaris (L1-2)
Cauda Equina
Anterior median fissure
Anterolateral fissure
Posterior
median sulcus
Posterolateral
sulcus
Posterior
intermediate
sulcus
Fasciculus
cuneatus
Fasciculus
gracilis
Posterior surface of the spinal cord
Spinal Cord
Meninges
Periosteum of Vertebra
- Epidural Space ----------------- epidural anesthesia
Dura Mater Spinalis
Arachnoid Membrane
- Subarachnoid Space -------- Lumbar Puncture
Spinal Anesthesia
Pia Mater Spinalis
- Denticulate Ligament --------- Cordotomy
- Filum Terminale
Meninges of
the spinal cord
• Dura mater
• Arachnoid membrane
• Pia mater
Denticulate ligament
- specilization of the pia mater
- landmark for cordotomy
Meninges of the spinal cord
Meninges of the spinal cord
Lumbar Puncture – lumbar (terminal) cistern
Spinal Cord
Vascular Supply
Arterial Supply
- Spinal Arteries
Anterior (1) & Posterior (2) Spinal Artery
from Vertebral artery
- Radicular Arteries ----- Segmental arteries
from Vertebral, Ascending Cervical, Intercostal and
Lumbar Artery
Venous Drainage
- Longitudinal & Radicular Veins
to Intervertebral veins ---- to Internal Vertebral Venous Plexus
to external vertebral venous plexus ---- to segmental veins
5. Adamkiwicz artery
anterior spinal artery
segmental arteries
Spinal Cord
Internal Structure
White Matter
Anterior Funiculus (Anterior White Column)
Posterior Funiculus (Posterior White Column)
Fasciculus Gracilis & Fasciculus Cuneatus
Lateral Funiculus (Lateral White Column)
Gray Matter
Anterior Horn --------------Posterior Horn -------------Lateral Horn ----------------Gray Commissure --------
motor
sensory
autonomic (sympathetic)
anterior and posterior
• Resembles a butterfly.
• 2 lateral gray masses connected by the gray
commissure.
• Posterior projections are the posterior or dorsal horns.
• Anterior projections are the anterior or ventral horns.
• In the thoracic and lumbar cord, there also exist lateral horns.
Gray Matter
• Posterior horns contain
interneurons.
• Anterior horns contain some
interneurons as well as the cell
bodies of motor neurons.
– These cell bodies project their axons via the ventral roots of the spinal
cord to the skeletal muscles.
– The amount of ventral gray matter at a given level of the spinal cord is
proportional to the amount of skeletal muscle innervated.
Gray Matter
• Lateral horn neurons are sympathetic
motor neurons serving visceral organs.
– Their axons also exit via the ventral root.
• Afferent sensory fibers carrying info
from peripheral receptors form the
dorsal roots of the spinal cord. The
somata of these sensory fibers are
found in an enlargement known as a
dorsal root ganglion.
• The dorsal and ventral roots fuse to
form spinal nerves.
1. posterior horn
2. anterior horn
3. intermediate zone
(intermediate gray)
4. lateral horn
5. posterior funiculus
6. anterior funiculus
7. lateral funiculus
8. Lissauer's tract
9. anterior median
fissure
10. posterior median
sulcus
11. anterolateral
sulcus
12. posterolateral
sulcus
13. Posterior
intermediate
sulcus
cervical enlargement (C8)
lumbal enlargement (L3)
thoracic cord (T8)
sacral cord (S1)
Spinal Cord
Internal Structure
Principles of Cord Organization
1) Longitudinal Arrangement
Fibers (White Matter) ------------- White Column
Cell Groups (Gray Matter) ------- Gray Column
2) Transverse Arrangement
Afferent & Efferent Fibers
Crossing (Commissural and Decussating) Fibers
3) Somatotopical Arrangement
Columnnar arrangement
somatotopical arrangement
Spinal Cord
Internal Structure
Laminae of Rexed
Lamina I ---------- posteromarginal nucleus
Lamina II ---------- substantia gelatinosa of Rolando
Lamina III, IV ----- nucleus proprius
Lamina V, VI
Lamina VII --------- intermediate gray
intermediolateral cell column (ILM)
Clarke’s column (Nucleus dorsalis)
intermediomedial cell column (IMM)
Lamina VIII
Lamina IX ---------- anterior horn (motor) cell
Lamina X ----------- gray commissure
Laminae of Rexed
White Matter
• Myelinated nerve fibers.
• Allows for communication btwn the brain and spinal cord or btwn different regions of
the spinal cord.
• White matter on each side of the cord is divided into columns or funiculi.
– Typically, they are ascending or descending.
» What does that mean?
Spinal Cord
Tracts
Ascending Tracts
Modality: Touch, Pain, Temperature, Kinesthesia
Receptor: Exteroceptor, Interoceptor, Proprioceptor
Primary Neuron: Dorsal Root Ganglion (Spinal Ganglion)
Secondary Neuron: Spinal Cord or Brain Stem
(Tertiary Neuron): Thalamus (Ventrobasal Nuclear Complex)
Termination: Cerebral Cortex, Cerebellar Cortex, or
Brain Stem
Spinal Cord
Tracts
Ascending Tracts
Posterior White Column-Medial Lemniscal Pathway
Spinothalamic Tract
Spinoreticular or Spinoreticulothalamic Tract
Spinocerebellar Tract
Spinomedullothalamic Tract
Cervicothalamic or Spinocervicothalamic Tract
Spino-olivary Tract
Spinotectal Tract
medial lemniscus
lemniscal decussation
internal arcuate fiber
posterior white column
posterior root
Posterior White Column Medial Lemniscal Pathway
- ipsilateral loss of discriminative touch
sensation and conscious proprioception
below the level of lesion
spinothalamic
tract
decussation
anterior white
commissure
posterior root
Spinothalamic Tract
- contralateral loss of pain and temperature
sensation below the level of lesion
Descending tracts
Lateral pathway
-Voluntary movement of distal muscles
-Direct cortical control
Ventromedial pathway
-Pose and antigravitational movements
-Indirect cortical (stem) control
Corona Radiata
lnternal Capsule, Posterior Limb
Crus Cerebri, Middle Portion
Longitudinal Pontine Fiber
Pyramid
CR
Pyramidal Decussation
Corticospinal Tract
IC
- Lateral and Anterior
LPF
Corticospinal Tract
Pyr
PD
- ipsilateral UMN syndrome
at the level of lesion
ACST
LCST
Spinal Cord
Tracts
Descending
Tracts
from
Brain Stem
ventromedial
pathway
dorolateral
pathway
Spinal Nerves
• 31 nerves connecting the
spinal cord and various
body regions.
»
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8 paired cervical nerves
12 paired thoracic nerves
5 paired lumbar nerves
5 paired sacral nerves
1 pair of coccygeal nerves
Spinal Nerves
• Each connects to the spinal cord by 2
roots – dorsal and ventral.
• Each root forms from a series of
rootlets that attach along the whole
length of the spinal cord segment.
• Ventral roots are motor while dorsal
roots are sensory.
Spinal Nerves
• The 2 roots join to form a
spinal nerve prior to exiting
the vertebral column.
• Roots are short and
horizontal in the cervical
and thoracic regions while
they are longer and more
horizontal in the sacral and
lumbar regions.
• After emerging from its intervertebral foramen, a spinal nerve divides into
• dorsal ramus,
• ventral ramus, and
• meningeal branch that recurs to supply the meninges and associated blood vessels.
• Each ramus is mixed.
• Joined to the base of the ventral rami of spinal nerves in the thoracic region are the rami
communicantes. These are sympathetic fibers that we’ll deal with shortly.
• Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the
rest of the body trunk and the limbs.
Reflex Arcs
• A reflex is a rapid, predictable
motor response to a stimulus.
Unlearned and involuntary.
• Example?
• Components of a reflex arc:
– Receptor  site of stimulus
– Sensory neuron  transmits afferent
info to CNS
– Integration center  1 or more
interneurons
– Motor neuron  transmits efferent
signals to effector
– Effector  muscle or gland
Reflexes
• Reflexes involving skeletal muscles and somatic motor neurons are
somatic.
• Reflexes controlled by autonomic neurons are autonomic.
• Spinal reflexes are integrated w/i the spinal cord while cranial reflexes
are integrated in the brain.
• Reflexes may be inborn or learned.
• Reflexes may be monosynaptic or polysynaptic.
– Difference?
Spinal Cord
Syndrome
Predominantly Motor Syndromes
• Poliomyelitis (Infantile Paralysis)
- viral infection of lower motor neuron
- LMN syndrome at the level of lesion
• Amyotrophic Lateral Sclerosis (ALS)
- combined LMN and UMN lesion
- LMN syndrome at the level of lesion
- UMN syndrome below the level of lesion
- Lou Gehrig’s disease in USA
Spinal Cord
Syndrome
1. corticospinal
tract
2. lower motor
neuron (LMN)
Amyotrophic Lateral Sclerosis
Spinal Cord
Syndrome
Amyotrophic
Lateral Sclerosis
(ALS)
Lou Gherig’s
Disease
Stephen Haking (1946- )
British Physicist, A Brif History of Time
Spinal Cord
Syndrome
Brown-Sequard syndrome
(spinal cord hemisection)
Major Symptoms
1. ipsilateral UMN syndrome below the level of lesion
2. ipsilateral LMN syndrome at the level of lesion
3. ipsilateral loss of discriminative touch sensation and
conscious proprioception below the level of lesion
(posterior white column lesion)
4. contralateral loss of pain and temperature sensation
below the level of lesion (spinothalamic tract lesion)
Spinal Cord
Syndrome
3
3'
1
3'
1
3
1
1'
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2
2'
5'
4
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5
1'
3
3
1
Brown-Sequard Syndrome (Spinal Cord Hemisection)