SPINAL CORD
INTERNAL STRUCTRE
BY
DR SHIVRAM BHAT
TRANSVERSE SECTION
AT DIFFERENT LEVELS
Grey matter
INTERNAL STRUCTURE
•H shaped Grey matter in the centre
& white matter in the periphery.
GREY MATTER
•It consists of nerve cells, neuroglia &
blood vessels.
• The grey matter presents a pair of
anterior grey column (ventral horns)
& posterior grey column (dorsal
horns. Lateral grey column – in some
parts.
White matter
LGC
PGC
AGC
•The grey matter of right & left halves are connected
across in the midline by grey commissure & traversed by
central canal.
NUCLEI OF SPINAL CORD- Columnar arrangement
Anterior grey column: Lower motor neurons (α, β, )
are arranged in 3 groups of longitudinal columns in
cervical & lumbosacral enlargements. Medial, lateral
&central.
• Medial – whole length –
VM, DM- skeletal
Retro dorso
muscles of the trunk.
lateral N
• Lateral – Cervical &
Dorso
lumbosacral
lateral N
enlargements- VL, DL Ventro
& RDL. Limb muscles. lateral N
• Central – Cervical &
lumbosacral- phrenic
Dorsomedial N Trunk
Central N
nerve nucleus
muscles
Ventromedial N
Posterior grey column:
4 main sets of nuclei are seen.
• Postero marginal nuclei: Receives some
incoming dorsal root fibers.
• Substantia gelatinosa of Rolando:
Present through the entire length of
spinal cord- Relay station for pain and
temperature fibers. The axons give rise
to lateral spino thalamic tract.`
• Nucleus proprius: Present through the
entire length of the cord. Concerned
with sensory associative mechanisms.
• Nucleus dorsalis:C8- L3 segments –
unconscious proprioceptive impulses to
the cerebellum- post spino cerebellar
tract. Visceral afferent Nu.
Lateral grey column:
• Intermediolateral: Acts as
both efferent and afferent
nuclear columns. Seen at 2
levels T1- L2 segments
(pregang. Symp fib,
thoracolumbar outflow) and
S2-S4 segments (pregang.
Symp fib, for pelvic viscera).
• Intermedio medial: Mostly
internuncial neuronal column.
LAMINAR CONCEPT OF SPINAL GREY MATTER:
• LAMINA I : post marginal nucleus
• LAMINA II: Substantia gleatinosa of
Rolando
• LAMINA III & IV: Nucleus proprius.
• LAMINA V & VI: Corresponds to base
of dorsal column.
• LAMINA VII: Between dorsal &
ventral – intermedio medial and lateral
• LAMINA VIII: Ventral horn (DMN,
VMN)
• LAMINA IX: Lateral group of nuclei.
Supply the skeletal muscle.
• LAMINA X: Surrounds the central
canal. Contains decussating axons.
SENSORY RECEPTORS: Peripheral endings of
•
•
•
•
afferent fibers which receive impulses.
Exteroceptors: Respond to stimuli from external
environment – pain, temp, touch and presure.
Proprioceptors: Respond to stimuli from in deeper
tissues – contraction of muscles, movements, position
and pressure.
Interoceptors: From viscera, gland, blood vessel, carotid
sinus.
Special sense receptors: Concerned with vision, hearing,
smell and taste.
NUCLEI & FUNCTIONS
TRANSVERSE SECTION
ARRANGEMENTS OF FIBERS IN THE FUNICULI
IN THE ANTERIOR FUNICULI:
• Peripheral
• Intermediate
• Deep
Medial reticulospinal tract
Spino-olivary
Anterior spino
thalamic
Olivo spinal
Anterior cortico
spinal
Tectospinal
Lat. vestibulo
spinal
IN THE LATERAL FUNICULI:
• Peripheral
• Intermediate
Lateral cortico spinal
Rubro spinal
Post. Spino
cerebellar
Ant. Spino
cerebellar
Lateral spino thalamic
Lateral reticulo spinal
IN THE DORSAL FUNICULI:
• Fasciculus gracilis
• Fasciculus cuneatus.
Fasciculus gracilis
They convey the axons of
Fasciculus cuneatus
first order sensory
neurons from the cells of
the dorsal root ganglia.
Fibers of dorsal root and their termination:
• All modalities of sensations
(Exteroceptive,
proprioceptive and
interoceptive) reach the
spinal cord by way of
dorsal nerve roots.
• Dorsal root presents near
the intervertebral foramen
a spinal ganglion which
contains T shaped unipolar
neurons with peripheral
and central process.
SPINAL GANGLION/DORSAL
ROOT GANGLION
CENTRAL PROCESS
PERIPHERAL PROCESS
TRACTS:
Connection of nerve fibers that
connects two masses of grey
matter within the CNS.
DESCENDING TRACTS:
1. PYRAMIDAL:
Lateral corticospinal tract
Anterior cortico spinal tract
2. EXTRAPYRAMIDAL
TRACT:
Rubro spinal
Medial & lateral reticulo spinal
Olivospinal
Vestibulospinal
tectospinal
Pyramidal/ Lateral corticospinal
• Formed by the axons of
pyramidal cells in the motor
area of the cerebral corterx +
cells of premotor area also.
Posterior limb of internal
capsule
midbrain
pons
medulla 80%
cross to the opposite side
(Pyramidal decussation) enter
the lateral column of white
matter & form the lateral
corticospinal.
• Most of the fibers terminate
at the anterior horn cells
INTERNAL
CAPSULE
MIDBRAIN
PONS
MEDULLA
CROSSING
Pyramidal/ Anterior corticospinal
• 20% of the fibers which
donot cross enter anterior
white column to form
anterior corticospinal tract.
• The fibers also cross at
appropriate levels and reach
grey matter of opposite half
of spinal cord.
• Found only in primates
including man.
INTERNAL
CAPSULE
MIDBRAIN
PONS
MEDULLA
CROSSING
Functional significance of pyramidal tract:
• Concerned with the skillful, voluntary movements of
non-postural type affecting mainly the flexor muscles
of distal part of upper and lower extremities.
• Controls voluntary movements of opposite half of the
body through anterior horn cells.
• Facilitatory for flexors and inhibitory for extensors.
• LESION: Above the level of decussation cause
contralateral paralysis. Below the level- ipsilateral.
UMN type: loss of power of voluntary movements.
hypertonia, exaggerated tendon reflexes,
superficial reflexes are lost.
Extrapyramidal tracts:
Rubrospinal tract:
From red nucleus in midbrain -ant horn cells in the
spinal cord (X).
Reticulospinal tracts:
1. Medial reticulospinal : reticular formation in pons,
uncrossed terminate in spinal cord.
2. Lateral reticulospinal : reticular formation in the
medulla oblongata, crossed & uncrossed, spinal cord.
Olivospinal tract:From inferior olivary nucleus in medulla
oblongata, uncrossed to anterior horn cells of spinal
cord.
Vestibulospinal tract: From vestibular nucleus in
the pontomedullary junction uncrossed to anterior
horn cells of spinal cord.
Tectospinal tract: From superior colliculus in the
midbrain, cross (dorsal teg decussation)to anterior
horn cells of spinal cord.
Descending tracts
Ascending tracts:
• The 1st order neurons start in the dorsal root ganglia
which has pseudounipolar cells.
• The peripheral process of these cells from the sensory
fibers of peripheral nerves which carry various types of
sensations from sensory end organs.
• The central process of the neurons in the dorsal root
ganglia enters the spinal cord through dorsal nerve root
and terminate either by synapsing with cells in posterior
grey column of spinal cord / at higher level in the
medulla i.e. nucleus nucleus gracilis/cuneatus.
• The 2nd order neuron starts from here and end in
thalamus or cerebellum.
• 3rd order starts from here and ends projects into sensory
areas in the cerebral cortex.
Lateral spinothalamic tract:
sensation of pain &temp
• 1st order neuron - dorsal root
ganglia- synapse with
neurons in the grey matter of
lamina II & III.
• 2nd order neuron cross to opp
side and ascend as lateral
spinothalamic tract.
• Lesion of lateral spino
thalamic tract produces
contralateral loss of pain and
temp of the body below the
lesion.
Thalamus
Dorsal root
ganglia
Crossing
Anterior spinothalamic tract:
crude touch &pressure
• 1st order neuron - dorsal
root ganglia- synapse
with neurons in the grey
matter of lamina III &
IV.
• 2nd order neuron cross to
opp side and ascend as
anterior spinothalamic
tract.
ANTERIOR
SPINOTHALAMIC
CROSS
DORSAL ROOT
GANGLIA
Fasc. gracilis (Tract of Goll): conscious
proprioception, & discriminatory
touch(lower thoracic, lumbar, sac,
cocc)
• 1st order neuron - dorsal root
ganglia- do not synapse with neurons
in the grey matter. Ascend in the
posterior column of white matter,
Nucleus
synapse with neurons of nucleus
gracilis
gracilis
• 2nd order neuron , cross, ascend and
relay in the thalamus.
• 3rd order neuron goes to the sensory
area in the cerebral cortex.
Fasc. Cuneatus (Tract of Burdach):
unconscious proprioception, &
exteroceptive touch(upper thoracic,
cervical segment)
• 1st order neuron - dorsal root
ganglia- do not synapse with
neurons in the grey matter. Ascend
in the posterior column of white
Nucleus
matter, and synapse with neurons cuneatus
of nucleus cuneatus
• 2nd order neuron ,cross and relay in
the thalamus. Proprioceptive goes
to the cerebellum
• 3rd order neuron goes to the sensory
area in the cerebral cortex.
• Spino tectal.
• Spino reticular.
• Spino cerebellar- anterior and posterior.
Ascending tracts
LESIONS: ( AFFERENT SYSTEM)
• Dorsal nerve roots: slip disc, extramedullary
tumour, inflammation. Complete destruction –
ipsilateral and segmental loss of all modalities of
sensation.
• Posterior white funiculus: Complete lesion – loss
of position sense, vibratory sense, discriminative
touch on the same side. Patient walks with legs
apart and eyes fixed to the ground.
• Spinothalamic tracts: involvement of lateral –loss
of pain and temp on the opp side below the lesion.
• Syringomyelia: Cavitation of the central canal
affecting the cervical enlargement of the cordbilateral and segmental loss of pain and
temperature.
LESIONS: ( EFFERENT SYSTEM)
• LMN lesion: results in hypoactive muscle, and
reduction in muscle tone ---no stretch reflex.
Muscle fasciculation, twitching or contractions of
groups of muscle fibers. Muscle undergoes
wasting or atrophy. (FLACCID PARALYSIS)
• UMN lesion: Have a net overall inhibitory effect
on muscle stretch reflex.----Paralysis of skeletal
muscle with muscle stretch or deep tendon reflex
that are hypertonic/ hyperactive. (SPASTIC
PARALYSIS). Disuse atrophy of muscles