SPINAL CORD

Professor İlkan TATAR, M.D., Ph.D.

ilkantatarmdphd@gmail.com
• Central Nervous System

• Afferent impulses à brain

• Nerve signals à body

• Autonomic cell bodies

• Lies within the vertebral canal

(occupies the upper 2/3)
 EXTERNAL FEATURES

Foramen magnum

L1-2 (adult)

•Medulla oblongata

•Adult: ♂ 45 cm, ♀ shorter

FM MO
Vertebral canal
*upper 2/3

L1-2
 CERVICAL ENLARGEMENT
(INTUMESCENTIA CERVICALIS)
&
LUMBAR ENLARGEMENT
(INTUMESCENTIA LUMBOSACRALIS)

• Cervical (C3–T2 segments)

38 mm
o (Brachial plexsus)

• Lumbosacral (L1–S3 segments)

35 mm
o (Lumbosacral plexus)

o Conus Medularis
Cervical
enlargement

Lumbar Conus
enlargement medullaris
Cervical
enlargement
(C3-T2)

Lumbar
enlargement
(C3-T2)
Meninges
• Continuation of the cranial meninges (D-A-P)

• Spinal dura mater

• Spinal arachnoidea mater
• Spinal pia mater
• Dura mater: thickest and most external
• Arachnoid mater: internal surface of the dura mater;
• Pia mater: invests the spinal cord Pia
Arachnoid
Dura
 Epidural Space:
Btw dura & V.C.
Subdural Space:
Potential space
Subarachnoid Space:
Fluid filled

L1
“Epidural Space” P
“Subdural Space” A
“Subarachnoid Space”
D
Epidural Space, Subdural Space, Subarachnoid Space
DURA MATER & ARACHNOİD MATER
à S2
PİA MATER S.
à beyond the conus medullaris

Filum
terminale
•“Filum terminale (internum – filum terminale pial
part)”

•S2 à “Coccygeal lig. (Filum terminale externum

– filum terminale dural part)”
à coccyx
•∽ 20 cm
Lig.
coccygeum
Denticulate ligament

Sub-pial connective tissue

(triangular processes)
Fixed to dura

Btw ventral & dorsal spinal roots

• Ventral (anterior) median fissure
• Dorsal (posterior) median sulcus
• Anterolateral sulcus
• Posterolateral sulcus
• Dorsal intermediate sulcus (Septum medianum posterius)
(Cervical & upper thoracic segments)

posterior

anterior
 Segmental Structure
• The region of the SC associated
with a particular pair of spinal
nerves is called a spinal
segment

• SC part à SEGMENT

33 segments ?
• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 3 coccygeal (2 rudimental)
 31 pairs of spinal nerves are
named according to their
associated vertebrae

• The first cervical nerve (C1) emerges btw

occipital bone – 1st CV

• Cervical nerves emerge from the

intervertebral foramens above their
respective vertebrae.
(C8 emerges btw 7th CV – 1st TV)

• All remaining spinal nerves emerge from

the intervertebral foramens below their
respective vertebrae.
 SPINAL NERVES
Dorsal (Posterior) root (sensory):
enter the cord along the posterolateral
sulcus, contains sensory neurons
(AFFERENT)

Ventral (Anterior) root (motor):

Emerges from the anterolateral sulcus,
housing the axons of motor neurons
(EFFERENT)
Within the vertebral canal; Rootlets

Dorsal root

Ventral root

Anterior median fissure

Spinal Ganglia (Dorsal Root Ganglia)
• large groups of neurons
• on the dorsal spinal roots
• in the intervertebral foramina
 Spinal Nerve
• Ventral & dorsal roots (covered by pia & arachnoid) unite in
their intervertebral foramina
à SPINAL NERVE (mixed)
• During development, the vertebral column elongates more rapidly
than the spinal cord.
• Because the spinal cord is much shorter than the vertebral column,
the roots of spinal nerves become longer and pass inferiorly

https://slideplayer.com/slide/8412977/
Cauda equina
• The dorsal and ventral
roots of lumbar, sacral,
and coccygeal nerves
pass inferiorly to reach
their associated
intervertebral foramenà
CAUDA EQUİNA
(horse’s tail).

• Around filum terminale

• Lumbar cistern
 spinal nerve
“has 4 functional components”

• GSE: General somatic efferent (motor: skeletal musc.)

• GSA: General somatic afferent (sensory: touch, pressure,
pain)
• GVE: General visceral efferent (motor: smooth & cardiac
musc.)
• GVA: General visceral afferent (sensory: organs, glands)
 spinal n.
• Each mixed spinal n., exit from the intervertebral foramina
& branch into
à ventral (anterior) ramus & dorsal (posterior) ramus

main trunk
posterior r.

anterior r.
• Anterior ramusà
Plexus
Thoracal segments; intercostal n.
• Posterior ramusà
Deep muscle groups
Ventral ramus;
àreceives a gray ramus
communicans from its
corresponding sympathetic chain
ganglion.

each ventral ramus from T1- L2,3

à provides a white ramus
communicans to its
corresponding sympathetic
chain ganglion

These connections carry

postganglionic and preganglionic
sympathetic fibers

Additionally, ventral rami S1–S3

also provide spinal preganglionic
parasympathetic fibers.
 Metamer/ Dermatome/ Axial Line
• Metamer: Structures innervated by one spinal nerve
• Dermatome: Area of skin innervated by cutaneous axons in the
distribution of a single spinal nerve
• Axial line: Line between two adjacent dermatomes that are not
represented by immediately adjacent spinal levels.

C5
T1
T2
Axial line
Dermatomes
INTERNAL ORGANIZATION
• Grey matter (inner): Neuronal cell bodies
• White matter (outer): Myelinated axons
 GREY MATTER
Transvers section;
• Ventral horn
• Dorsal horn
• Lateral (intermediate)horn (T1 – L3 (L2)

DH LH

VH
 3D;
• Ventral hornà ventral column
• Dorsal horn à dorsal column
• Lateral horn à lateral column
 Central Canal
• Grey matter surrounds the central canal
• Anterior; ventral grey commissure
• Posterior; dorsal grey commissure

• CSF
 Laminae
• Grey matterà On the basis of neuronal size, shape and
features divided into 10 zones (Rexed’s Laminae)

http://medicine.academic.ru/134796/Rexed_laminae
 Laminae I – IV (dorsal horn)
• Lamina I: Marginal nucleus
• Lamina II: Substantia gelatinosa (Rolando)
• Lamina III & IV: Nucleus proprius

• Main site of termination of cutaneous primary afferent

terminals
Laminae V & VI (base of the dorsal horn)
• Most of the proprioceptive primary afferents
• Corticospinal projections from motor & sensory cortex
• Involvement in the regulation of movement
 Lamina VII (lateral horn)
• Connections with Mesencephalon & Cerebellum
• Intermediate zone

• posterior thoracic nucleus (Clarke’s nuc.) à C8-L3 Proprioceptive fibers

(give rise to dorsal spinocerebellar tract)
• intermediolateral nucleus à T1-L2: preganglionic sympathetic neurons
• intermediomedial nucleus à full length of the cord, control of visceral motor
neurons

• Sacral parasympathetic nucleus à located at sacral levels 2–4.

à preganglionic neurons of the sacral outflow of the parasympathetic
nervous system are also considered to belong to Rexed lamina VII.
 Lamina VIII (base of the ventral horn)
• Mass of propriospinal interneurons
• Receives terminals from adjacent laminae, commissural fibers from
contralateral LVIII, descending connections from eff. pathways
(interstitiospinal, reticulospinal, vestibulospinaltracts, medial longitudinal fasciculus)
• Axons from these interneurons influence α motor neuron activity bilaterally
à skeletal muscle contraction coordination
Lamina IX
• α & γ motor neurons & many interneurons
• Large α motor neurons supply motor end-plates of extrafusal
fibers in striated muscles
• Smaller γ motor neurons à intrafusal muscle fibers
 Lamina X
• Surrounds the central canal
• Believed to be associated with autonomic n. s.
• Aff axons carried by dorsal root à synaps
I à marginal nuc.
II à subst. gelatinosa
III & IV à nuc. proprius
V & VI à proprioceptif aff
VII à nuc. intermediolat
nuc. intermediomed
nuc. thoracicus posterior)
VIII à α motor neuron
IX à α & γ motor neurons
X à aff axons from dorsal root
WHITE MATTER
Composed of myelinated & unmyelinated fibers
1) Brings information into the central nervous system (CNS) and
transmit it to higher levels.
2) Transmits information from the higher levels to the spinal cord and
to muscles and glands.

https://www.easynotecards.com/notecard_set/28662
WHITE MATTER
• Dorsal funiculus
• Lateral funiculus
• Ventral funiculus
• Ventral white commissure
• Dorsal white commissure

https://www.easynotecards.com/notecard_set/28662
• Dorsal funiculus is bounded by the dorsal median and dorsolateral sulci
• Lateral funiculus is between the dorsolateral and ventrolateral sulci
àbetween the dorsal and ventral rootlets.
• Ventral funiculus is between the ventrolateral sulcus and the ventral median
fissure.

Moreover, the ventral funiculus houses the ventral white commissure, the
region of decussation for the spinothalamic tracts.

DF

LF

VF
• Cervical and upper thoracic aspects of the DORSAL FUNICULUS (C1-T6)
à subdivided by the dorsal intermediate sulcus
• à medial fasciculus gracilis & lateral fasciculus cuneatus.
Within the funiculi, the nerve fibers that have similar destinations are
arranged in bundles à tractus OR fasciculi
• ASCENDING TRACTS (AFFERENT): transmit sensory information to
higher centers
• DESCENDING TRACTS (EFFERENT): transfer motor information
originating at higher centers
• The intersegmental tracts: carry information btw spinal cord
segments, à managing intersegmental spinal
reflexes.
 Ascending Aff Carried by Dorsal Root
• Med; Thick myelinated à Proprioceptive
• Lat; Thin myelinate & unmyelinated à Pain, Heat, Light touch

• ascending & descending tracts in the white matter (before entering the
grey matter) à collaterals à within the Dorsolateral Tract (Lissauer’s)
à superficial laminae
• thick à few segments up & down à deep laminae
 Spinal Reflexes
specific stimulus àInvoluntary response

•Modulated by descending connections (brain stem &

cortex) of α motor neurons.

•afferent information from the peripheral structures (muscle,

joint, skin) modulated in the spinal cord à
motor response
 Monosynaptic Reflex Arc
• Sensory signal from peripheric (stretch) receptors
(intrafusal muscle fibres) à α motor neuron à effector
structures

• Direct synapse with α motor neuron à Monosynaptic

(stretch)
• If there is an interneuronà Polysynaptic (flexor)

• intrasegmental àlimited to a single cord level: patella

reflex
• intersegmental à involve several cord segments:
postural
Monosynaptic Reflex Arc

http://biology-forums.com/index.php?action=gallery;sa=view;id=8842
 Deep Tendon Reflex
(myotactic reflex)

• Stretch applied to a muscle

à the intrafusal muscle
fibers stretch
à with group 1a aff fibres

à α motor neuron of SC

à extrafusal muscle fibres

à contraction

http://what-when-how.com/neuroscience/the-spinal-cord-organization-of-the-
central-nervous-system-part-5/
 Polysynaptic Reflex Arc

http://biology-forums.com/index.php?action=gallery;sa=view;id=8842
 Golgi Tendon Organı
• Lies in the origins-insertions of the skeletal muscle
• Proprioceptive sensory receptor senses changes in the
muscle tension
• Contraction à impulses carried by group 1b aff axons
à SC

Contrary to group Ia:

inhibits the α motor neuron of synergist musc.
activates the α motor neuron of antagonist musc.
http://what-when-how.com/neuroscience/the-spinal-cord-organization-of-the-
central-nervous-system-part-5/
 Flexor (Withdrawal) Reflex
(polysynaptic)
• Painful stimulation à stimulation of many motor neurons
• interneurons à nearby spinal segments mediate flexion of a limb at
several joints
• Connections to the contralateral side of the cord activate α motor
neuron à corresponding extensor muscles

• ipsilat: musc flex musc contrc. extans musc. inh

• contralat: ext musc contrc. flex. musc inh.
 Arteries
• vertebral a.
• circumjacent arteries
Vertebral a. posterior spinal aa.

anterior spinal a.

• posterior spinal a. x 2
• anterior spinal a. x 1
spinal (segmental)
branches à
üAscending cervical a.
üDeep cervical a.
üPosterior intercostal aa.
üLumbar aa.
üLateral sacral br.

•Intervertebral foramen
ààVentral & dorsal roots
àant & post radicular aa.

•anastomose
The anterior and posterior
spinal aa. are reinforced
along their length by 8-10
segmental medullary aa.

Largest:
a. radicularis magna
(artery of Adamkiewicz)
à lower thoracic or upper
lumbar region (usually on
the left side)
à supply the lower portion
of the SC (including the
lumbar enlargement)
Veins
Form a number of longitudinal channels;
• 2 pairs on posterior and anterior roots;
• 1 at the anterior median fissure (anterior spinal v.);
• 1 at the posterior median sulcus (posterior spinal v.).
à internal vertebral plexus in the epidural space
à external vertebral plexus
à major systemic veins, such as the azygos system
https://link.springer.com/chapter/10.1007/978-3-319-64789-0_21
 Connections;
• Intracranial veins
• Prostatic venous plexus
• Pelvic venous plexus