The Spinal Cord: DR - Satya

THE SPINAL CORD
DR.SATYA
Nervous system
Made up of nervous tissue
Neurons
Neuroglial cells
Parts of nervous system
1. Central nervous system (CNS)
Brain
Spinal cord
2. Peripheral nervous system (PNS)

Cranial nerves (From the brain -12 pairs) Lower end
of
Spinal nerves (from the spinal cord- 31
spinal cord
pairs)
Spinal cord
Lower cylindrical part of CNS
occupies upper 2/3rds of vertebral canal
45 cm in length , wt=30 gms
Extent:
Superior extent:
Upper border of atlas (CV1)or the level of origin
of 1st pair of cervical spinal nerves
Continues above with medulla oblongata
Inferior extent:
ends at the lower border of L1
tapering end is called Conus medullaris
Filum terminale is attached to the tip
Coverings( spinal meninges) - 3
1. Dura mater(pachymeninx)
2. Archnoid mater
3. Pia mater
the arachnoid & pia mater

together called leptomeninges
Figure 12.30b
Coverings of spinal cord Spinal meninges
Dura mater
Thick, fibrous, outermost covering
Continues superiorly with the dura mater of brain
Inferiorly ends at the lower border of S2 vertebra

Arachnoid mater:
Thin, transparent lies deep to the dura mater
Separated from the underlying pia mater by the subarachnoid space which
contains CSF
Extends inferiorly up to the S2 vertebra

Pia mater:
Inner most covering
Inferiorly extends up to the lower border of LV1
Continues below as filum terminale

SPINAL MENINGES
Coverings & spaces
External(outside) to dura
epidural space
Deep to Dura(i.e between dura & arachnoid)

subdural space
Deep to Arachnoid(i.e betwwen arachnoid & Pia)

subarachnoid space-contains CSF
The denticulate ligaments
Thickening of the pia mater
Project laterally and fuse with the arachnoid and inner

surface of the dura mater between the anterior and
posterior nerve roots - Surgical importance
Extending along the length of the SC, protect it against

shock and sudden displacement
Filum terminale
Made up of(extension of) pia
mater, 20 cm in length
Begins at the apex of conus

medullaris
pierces the dural sheath at S2

level and inferiorly attached to
the dorsum of coccyx
And thus has two parts

Internum -15 cm
Externum -5 cm
Enlargements
Two enlargements
Cervical & Lumbar
Due to more gray matter
Responsible for brachial and

lumbar plexus
2 Enlargements:
1. Cervical enlargement
C3 to T2 spinal segments
arise nerves supplying the upper limb
2. Lumbar enlargement
L1 to S3 spinal segments
give rise to nerves supplying the lower
limb
Conus medullaris
Conical ending of
the cord
Central canal is
dilated to form
terminal ventricle
Cauda equina
The bunch of lower
spinal nerves
(lumbar,sacral &
coccygeal nerves)
below the termination of
the spinal cord.
These nerves surround

the conus medullaris
and filum terminale and
resemble the tail of a
horse
Conus medularis and cauda equina
SPINAL SEGMENTS
Part of the spinal cord giving attachment to
the rootlets of one pair of spinal nerve.
31 segments are present
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 12
Spinal segment
Relation of the spinal segments
to vertebral spines
Cervical segments- 1( C4
at C3)
Upper thoracic -2
Lower thoracic -3 (T12 at
T9)
L 1 & L 2 - 10th Thoracic
L 3 & L 4 -11th
L5 -12th
Sacral and coccygeal L 1
lumbar
Spinal nerve
Dorsal(sensory) root (DR)
Ventral(motor) root (VR)
Spinal ganglion (SG) or

dorsal root ganglion (DRG)
Spinal nerve ( SN)
Spinal segment
31 segments & 31 pairs

(8+12+5+5+1)
Dorsal (sensory) root of spinal nerve
Has a ganglion containing

pseudounipolar neurons
with two processes
Peripheral process is
dendrite
Central process axon
Joins with ventral root to

form spinal nerve
Spinal nerve divides into

rami
Lumbar puncture(Spinal tap)
Skin
Supraspinous ligament
Interspinous ligament
Ligamentum flava
Dura mater
Arachnoid mater
external features
Features on anterior surface:
Anterior median fissure -
contains anterior spinal vessels
Anterolateral sulcus - rootlets of

ventral root of spinal nerves are
attached
Features on posterior surface:
Posterior median sulcus-
Posterolateral sulcus-
rootlets of dorsal root of spinal nerves

are attached
grey matter of the spinal cord
In Transverse section on arbitrary terminological
basis the grey matter is divided into-
1. Dorsal(posterior)
2. Intermediate(lateral) &
3. Ventral(anterior) horns or grey columns.
Based upon size, shape, packing density &

cytological features Rexed has classified the grey
matter into 10 laminae or cell layers.
grey matter- ventral horn or column
Medial, lateral and central groups
Medial group of nuclei:
Extends along most of the length
supply muscles of trunk.
Central group of nuclei:
In the cervical, lumbar and sacral segments
Phrenic nucleus C3 to C7
spinal Accessory nucleus C1 to C5
Lateral group of nuclei:
Found in enlargements
Ventrolateral nucleus- arm / thigh
Dorsolateral nucleus- fore arm / leg
Retrodorsal nucleus- hand / foot
white matter of spinal cord
The white matter consists primarily of longitudinally running nerve
fibres in form of tracts or fasciculi.
Fibres subserving related functions, or those with common origins or

destinations, are grouped together anatomically and are known as
tracts (fasciculi), which may be ascending, descending and
propriospinal.
Ascending tracts consist either of primary afferent fibres, that enter

the cord via the dorsal roots of spinal nerves, or fibres derived from
intrinsic spinal neurones, that carry afferent impulses to supraspinal
levels.
Descending tracts contain fibres that descend from the cerebral
cortex or brain stem nuclei to control the activity of spinal neurones.
Propriospinal tracts contain the axons of neurones that are localized

entirely to the spinal cord: they contain both ascending and
descending components, collectively mediating intersegmental
coordination.
white matter of spinal cord
made up of nerve fibres which may be
classified into 3 groups
1. Ascending or afferent or sensory fibres

-carry sensory impulses to the brain
2.Descending or efferent or motor fibres

-carry motor impulses from the brain
3.Intersegmental tracts
White matter
The spinal white matter in each half is
conventionally divided into three large,
masses namely:
dorsal(posterior)funiculus/white column
lateral funiculus/white column
Ventral(anterior) funiculus/white column
each funiculus contains specific named

tracts.
Tracts of Posterior funiculus
(post. white column tracts)
Ascending tracts: Descending tracts:
1.Fasciculus gracilis 1. Septomarginal tract

(tract of Goll )-
lies medially 2. Interfasiculus tract
2.Fasciculus cuneatus
(tract of Burdoch)-
lies laterally
1. Gracile tract
2. Cuneate tract
Descending-Yellow Ascending- Red
Tracts of Lateral funiculus
Ascending tracts Descending tracts
1. Dorsolateral tract of Lissauer 1. Lateral corticospinal

2. Posterior spinocerebellar
2. Rubrospinal
3. Anterior spinocerebellar
3. Lateral reticulospinal
4. Spino-olivary tract (lies at
the junction of ant.& lat.funiculi)
4. Descending autonomic
5. Lateral spinothalamic fibres( hypothalamo
spinal fibres)
6. Spinotectal( spinomesencephalic
pathway)
Anterior funiculus
Ascending tracts Descending tracts
1. Spinoreticular pathway 1. Olivospinal tract
2. Vestibulospinal
2. Anterior spinothalamic tract
3. Tectospinal
4. Anterior corticospinal
5. Medial reticulospinal
Ascending tracts
1. Fasciculus gracilis
2. Fasciculus cuneatus
3. Dorsolateral tract of Lissauer
4. Posterior spinocerebellar
5. Anterior spinocerebellar
6. Spino-olivary
7. Lateral spinothalamic
8. Spinotectal (spinomesencephalic)
9. Spinoreticular
10. Anterior spinothalamic
Descending tracts
1. Septomarginal tract
2. Interfasciculus tract
3. Lateral corticospinal tract
4. Rubrospinal tract
5. Lateral reticulospinal tract
6. Hypothalamospinal fibres
7. Olivospinal tract
8. Vestibulospinal tract
9. Tectospinal tract
10. Anterior corticospinal tract
11. Medial reticulospinal tract
Descending tracts
1. Corticospinal tracts (pyramidal tracts)
Major descending (motor) tracts concerned with the control of skeletal
muscles of body
2.Extra pyramidal tracts

All other descending tracts
Rubrospinal tract
Olivospinal tract
Vestibulospinal tract
Tectospinal tract
Reticulospinal tracts(lateral & medial)
Hypothalamospinal fibres
Functions of ascending tracts
Anterior spinothalamic Anterior spinocerebellar-
Simple(crude) touch and Proprioceptive impulses.
pressure
Posterior spinocerebellar-
Lateral spinothalamic proprioceptive impulses
Pain & temperature
Spinotectal
Fasciculus gracilis & Spinovisual reflexes.
Fasciculus cuneatus-
Proprioceptive impulses, Spinoolivary-Proprioceptive
vibration sense, fine touch, impulses via inferior olivary
tactile localization & nucleus
discrimination
Dorsolateral tract
pain & temperature
Descending tracts origin & functions
Tracts Origin Functions
Corticospinal Motor area of brain Controls voluntary

movements
Rubrospinal Red nucleus Facilitatory influence
of flexor tone
Reticulospinal Reticular formation voluntary movements
and muscle tone
Tectospinal Superior colliculus Spinovisual reflexes
Vestibulospinal Lateral vestibular Controls body

nucleus equilibrium
Olivospinal Inferior olivary Controls motor tone
nucleus
Blood supply to spinal cord
Arterial supply
By Posterior spinal arteries:
2 in no. - from posterior inferior

cerebellar artery.
By Anterior Spinal artery :
1 in no. - from vertebral artery
Spinal arteries are reinforced by

radicular arteries
Radicular Arteries are provided by

various arteries of the neck and the
trunk.
the radicular arteries at T 1 to
T11 vertebral are larger than the
rest.
largest is called Artery of
Adamkiewitz.
Blood supply to spinal cord
Blood supply of spinal cord
Anterior spinal artery
Spinal arteries
Ascending
cervical
Posterior
intercostal
Lumbar
Lateral sacral
Anterior spinal
artery
Sulcal artery
Vasa corona
Radicular
arteries

Venous return
The anterior and posterior spinal veins run along

the midline and along their respective nerve
rootlets to drain into the radicular veins.
The radicular veins drain into the epidural venous

plexus; which in turn drain into the external
vertebral venous plexus.
The External Vertebral Venous plexus empties into

the vertebral, intercostal & lumbar veins.

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THE SPINAL CORD

2. Peripheral nervous system (PNS)

the arachnoid & pia mater

Continues superiorly with the dura mater of brain

Inferiorly ends at the lower border of S2 vertebra

Extends inferiorly up to the S2 vertebra

Inferiorly extends up to the lower border of LV1

Continues below as filum terminale

Deep to Dura(i.e between dura & arachnoid)

Deep to Arachnoid(i.e betwwen arachnoid & Pia)

Project laterally and fuse with the arachnoid and inner

Extending along the length of the SC, protect it against

Begins at the apex of conus

pierces the dural sheath at S2

And thus has two parts

Due to more gray matter

Responsible for brachial and

arise nerves supplying the upper limb

give rise to nerves supplying the lower

These nerves surround

the rootlets of one pair of spinal nerve.

31 segments are present

Ventral(motor) root (VR)

Spinal ganglion (SG) or

Spinal nerve ( SN)

31 segments & 31 pairs

Has a ganglion containing

Joins with ventral root to

Spinal nerve divides into

Anterior median fissure -

contains anterior spinal vessels

Anterolateral sulcus - rootlets of

Features on posterior surface:

Posterior median sulcus-

rootlets of dorsal root of spinal nerves

Based upon size, shape, packing density &

Fibres subserving related functions, or those with common origins or

Ascending tracts consist either of primary afferent fibres, that enter

Propriospinal tracts contain the axons of neurones that are localized

1. Ascending or afferent or sensory fibres

2.Descending or efferent or motor fibres

each funiculus contains specific named

Ascending tracts: Descending tracts:

1.Fasciculus gracilis 1. Septomarginal tract

1. Dorsolateral tract of Lissauer 1. Lateral corticospinal

1. Spinoreticular pathway 1. Olivospinal tract

2.Extra pyramidal tracts

Tracts Origin Functions

Corticospinal Motor area of brain Controls voluntary

Vestibulospinal Lateral vestibular Controls body

By Posterior spinal arteries:

2 in no. - from posterior inferior

By Anterior Spinal artery :

1 in no. - from vertebral artery

Spinal arteries are reinforced by

Radicular Arteries are provided by

The anterior and posterior spinal veins run along

The radicular veins drain into the epidural venous