The spinal cord is cylindrical in shape and occupies the upper two-thirds of the vertebral canal. It has gray matter containing nerve cell bodies and white matter containing nerve fiber tracts. The spinal cord receives sensory information from the body via ascending tracts and sends motor commands via descending tracts. It is surrounded and protected by three layers of meninges and receives its blood supply from segmental arteries that branch from the anterior and posterior spinal arteries. Damage to the spinal cord can cause conditions like spinal shock and poliomyelitis that result in sensory loss and muscle paralysis below the level of injury.

1. SPINAL CORD
PROF DR NASARUDDIN ABDUL AZIZ
Management & Science University
dr_nasaruddin@msu.edu.my

2. OBJECTIVES
• describe the external structure of the spinal
cord,
• draw and describe the internal structure of
the spinal cord,
• draw and describe the ascending and
descending tracts within the spinal cord,
• describe the meninges surrounding the
spinal cord,
• describe the blood supply of the spinal cord,
• explain the clinical correlations of &
applications related to the spinal cord

3. Gross Appearance
• Cylindrical in shape
• Foramen magnum  L1/L2 (adult)
• L3 (newborn)
• Occupies upper ⅔ of vertebral canal
• Surrounded by 3 layers of meniges:
– dura mater
– arachnoid mater
– pia mater
• CSF in subarachnoid space

4. • Enlargements: cervical & lumbar
• Conus medullaris
• Filum termniale
• Anterior median fissure
• Posterior median sulcus
• 31 pairs of spinal nerves attached to it by
the anterior roots & posterior roots

11. Structure Of The Spinal Cord

14. Gray Matter
• H-shaped pillar with anterior & posterior gray
horns
• United by gray commissure containing the
central canal
• Lateral gray column (horn) present in
thoracic & upper lumbar segments
• Amount of gray matter related to the amount
of muscle innervated
• Consists of nerve cells, neuroglia, blood
vessels

15. Nerve cells in the anterior gray columns
• Large & multipolar
• Axons pass out in the anterior nerve roots
as α-efferents
• Smaller nerve cells are multipolar
• Axons pass out in anterior roots as -ɣ
efferents

16. Nerve cells in the posterior gray columns
• 4 nerve cell groups
• Substantia gelatinosa
– situated at the apex
– throughout the length of spinal cord
– composed mainly of Golgi Type II neurons
– receives afferent fibres concerning with pain,
temperature & touch from posterior root

17. • Nucleus proprius
– anterior to substantia gelatinosa
– present throughout the whole length of spinal
cord
– main bulk of cells in posterior gray column
– receives fibers from posterior white column
that are assoc with proprioception, 2-point
discrimination & vibration

18. • Nucleus dorsalis (Clark’s column)
– base of posterior column
– C8 – L3 / L4
– associated with proprioceptive endings
(neuromuscular spindles & tendon spindles)
• Visceral afferent nucleus
– lateral to nucleus dorsalis
– T1 – L3
– receives visceral afferent info

19. • Nerve cells in the lateral gray columns
• Formed by the intermediolateral group of
cells
• T1 – L2 / L3
• Cells give rise to preganglionic
sympathetic fibres
• In S2, S3, S4; they give rise to
preganglionic parasympathetic fibres

20. • The gray commissure & central canal
– connects the gray on each side
– central canal in the centre
– posterior gray commissure
– anterior gray commissure
– central canal present throughout
– superiorly continuous with the central canal of
medulla oblongata
– inferiorly, expands as terminal ventricle
– terminates within the root of filum terminale

21. White Matter
• Divided into
– anterior white column
– lateral white column
– posterior white column
• Consists of nerve fibres, neuroglia, blood
vessels
• White due to myelinated fibres

22. Tracts
• Ascending
• Descending
• Intersegmental

23. Ascending Tracts
• Fibres that ascend from spinal cord to
higher centres
• Conduct afferent information which may or
may not reach consciousness
• Information may be
– exteroceptive (pain, Tº, touch)
– proprioceptive (from muscles & joints)

24. Organization
• Ascending pathway that reach
consciousness consists of 3 neurons:
– 1st
-order neuron
– 2nd
-order neuron
– 3rd
-order neuron
• Branch to reticular formation
(wakefulness)
• Branch to motor neurons (reflex activity)

25. • Lateral spinothalamic tract
– pain & Tº
• Anterior spinothalamic tract
– light (crude) touch & pressure
• Fasciculus cuneatus
• Fasciculus gracilis
– discriminatory touch, vibration, info from muscles &
joints
• Anterior spinocerebellar tract
• Posterior spinocerebellar tract
– unconscious info from muscles, joints, skin, subcut

27. • Spinotectal tract
– spinovisual reflexes
• Spinoreticular tract
– info from muscles, joints & skin to reticular
formation
• Spino-olivary tract
– indirect pathway to cerebellum

28. Lateral spinothalamic tract
• Pain & temp pathways
• 1st
-order neurons
• Pain conducted by δ A-type fibres & C-type
fibres
• 2nd
-order neurons
– decussate to the opposite side
– ends in thalamus (ventral posterolateral nucleus
• 3rd
-order neurons
– ends in sensory area in postcentral gyrus

29. Anterior spinothalamic tracts
• Light (crude) touch & pressure pathways

30. Posterior white column
• Discriminative touch, vibratory sense,
conscious muscle joint sense (conscious
proprioception)

31. Posterior spinocerebellar tract
• Muscle joint sense pathways to
cerebellum
• Unconscious proprioception
• Muscle joint info from muscle spindles,
GTO, joint receptors of the trunk & lower
limbs
• Info is used by the cerebellum in the
coordination of movements &
maintenance of posture

32. Anterior spinocerebellar tract
• Majority of 2nd
-order neurons cross to the
opposite side
• Enter cerebellum through superior
cerebellar peduncle
• Info from trunk, upper & lower limbs
• Also carries info from skin & subcut tissue

33. Descending Tracts
• Lower motor neurons
• Upper motor neurons
• Corticospinal tracts
– concerned with voluntary, discrete, skilled
movements

35. • Reticulospinal tract
– facilitates or inhibits voluntary movement or reflex
activity
• Tectospinal tract
– reflex postural movements in response to visual
stimuli
• Rubrospinal tract
– facilitates activity of flexor muscles & inhibits
activity of extensor muscles
• Vestibulospinal tract
– facilitates extensor muscles, inhibits flexor
muscles

36. Meninges
• Dura mater
• Arachnoid mater
• Pia mater

38. Dura mater
• Dense, strong fibrous membrane
• Encloses the spinal cord & cauda equina
• Continuous above with meningeal layer of
dura covering the brain
• Ends at the level of S2
• Separated from wall of vertebral canal by
the extradural space
• Contains loose areolar tissue & internal
vertebral venous space

40. Arachnoid mater
• Delicate impermeable membrane
• Lies between pia and dura mater
• Separated from pia mater by
subarachnoid space
• Continuous above with arachnoid mater
covering the brain
• Ends on filum terminale at level of S2

41. Pia mater
• Vascular membrane
• Closely covers spinal cord
• Thickened on either side between nerve
roots to form the ligamentum denticulatum

42. Blood supply
Arteries of the spinal cord
• Anterior spinal artery
• Posterior spinal artery
• Segmental spinal arteries

44. Anterior spinal artery
• Formed by the union of 2 arteries
• From vertebral artery
• Supply anterior ⅔ of spinal cord
Posterior spinal arteries
• Arise from vertebral artery or posterior
inferior cerebellar arteries (PICA)
• Descend close to the posterior roots
• Supply posterior ⅓ of spinal cord

48. Segmental spinal arteries
• Branches of arteries outside the vertebral
column
• Gives off the anterior & posterior radicular
arteries
• Great anterior medullary artery of
Adamkiewicz
• Arise from lateral intercostal artery or
lumbar artery at any level from T8 – L3

52. Clinical correlations
Spinal shock
• Follows acute severe damage to the
spinal cord
• All cord functions below the level of the
lesion become depressed or lost
• Sensory impairment and flaccid paralysis
occur
• Segmental spinal reflexes are depressed
• Persists for less than 24 hours (may be as
long as 1 – 4 weeks)

53. Poliomyelitis
• Acute viral infection of the neurones of
anterior gray column
• Motor nuclei of cranial nerves
• Death of motor neurone cells → paralysis
& wasting of muscles
• Muscles of lower limb more often affected

54. • Spinal anaesthesia
• Extradural anaesthesia