1. Inha University Hospital Professor Yoon SH
Spinal Cord Anatomy
Inha University Hospital
Professor Yoon SH

2. Spinal Cord Anatomy Spinal cord is covered by pia, arachnoid, and dura
Cord suspended in dural sheath by denticulate ligament on each side
Attached along lateral surface of cord midway between dorsal and ventral roots

3. Spinal cord anatomy
Cord is enlarged in cervical (C4-T1) and lumbosacral regions (L2-S3)
Cord contains grey matter, white matter tracts, and central canal
Central canal lined by ependyma

4. Spinal cord anatomy Gray matter Dorsal root entry zone White matter
Vascular anatomy

5. Cross-section of the spinal cord with laminae of Rexed .
From G. Paxinos & C. Watson

6. Lamina of Rexed
Gray matter of spinal cord divided into ventral (anterior) and posterior (dorsal) horns
Posterior horn contains laminae 1-6
Lamina 1 gives origin to the pathway relaying information about pain to the thalamus
Lamina 2 and 3 (substantia gelatinosa) functions in regulating afferent input to the spinal cord.

7. Lamina of Rexed
Lamina 4 projects to the lateral cervical nucleus, the posterior column nuclei, and the thalamus (spinothalamic tract)
Lamina 5 and 6 receives proprioceptive input AND sensory information relayed by lamina 4. These are the sites of origin of ascending projections to higher centres.
From T1 to L3 is Clarke’s column, which is within lamina 6 and contains projections to the cerebellum via the dorsal spinocerebellar tract

8. Lamina of Rexed Anterior horn:
Lamina 9 contains motor neurons supplying the limbs and lamina 9M contains motor neurons supplying the trunk and neck. 9M is medial to 9.
Is further subdivided into flexor and extensors (flexors are dorsal) and into distal and proximal (distal is more lateral).

9. Lamina of Rexed
Laminae 7 and 8 contain interneurons involved in motor control and motor neurons that project to brain.
Lamina 8 is highly related to lamina 9M, and participates in movements of muscles in the head and neck.
Lamina 7 is related to lamina 9 and participates in limb muscle movement
Lamina 8 and 9M are highly developed in high cervical and thoracic segments controlling neck and trunk, whereas laminae 7 and 9 are highly developed in the spinal enlargements controlling the arms and legs

10. Lamina of Rexed
Intermediolateral cell column is present in thoracic and sacral segments, and is not considered part of the anterior or posterior horn
Contains neurons of origin of pre-ganglionic autonomic fibres
Lamina 10 surrounds central canal, and contains neurons that project to the opposite side of the cord.

11. White matter Divided into dorsal, lateral and ventral funiculi
Dorsal funiculus mostly comprised of ascending fibres whose bodies are located in dorsal root ganglia
Fibres are ipsilateral
Proprioception and fine discrimination (note that vibration is carried in both dorsal and lateral funiculi)

12. White matter – dorsal funiculus
Fasciculus gracilis medial to fasciculus cuneatus
F. gracilis from lower limbs and cuneatus from upper limbs
Note that lowest segmental innervation is most medial in gracilis and highest innervation is most lateral in cuneatus
Nucleus gracilis and cuneatus in medulla
There are descending fibres in dorsal funiculus which modify sensory input to the cord

13. White matter – lateral funiculus
Dorsolateral and lateral parts (fasciculi)
Dorsolateral contains lateral corticospinal tract (axons from contralateral frontal and parietal lobes); frontal fibres end in ventral horn
Lower limbs are lateral in tract and head is medial
Distal muscles are posterior to proximal muscles
Rubrospinal tract (from contralateral red nucleus) is rudimentary in humans; involved in increasing flexor tone

14. Lateral funiculus
Raphespinal tract in dorsal part of lateral funiculus; modifies painful stimuli from dorsal horn; fibres may begin in reticular formation of medulla
Hypothalamospinal tract arises from paraventricular nucleus of hypothalamus and end in pre-ganglionic autonomic segments T1-L3 and S2-S4

15. Lateral funiculus
spinocervical tract ascends and terminates in lateral cervical nucleus, which is rudimentary in humans (significance is unknown)
Dorsal spinocerebellar tract is present above L3; arises from Clarkes column and terminates in ipsilateral cerebellum; forms part of pathway of conscious proprioception from lower limb

16. Lateral funiculus Ventrolateral fasciculus
Spinothalamic tract has its nuclei in lamina 4,5,6 mostly.
Axons cross midline in ventral white commissure and traverse the ventral horn
End in thalamus
Collateral branches to reticular formation
Pain and thermal sensations
Fibres from lower limb are most superficial and from upper limb are deepest

17. Lateral funiculus
Ventral spinocerebellar tract arises from dorsal horn and border cells of ventral horn of lumbosacral cord
Crossed fibres
Ascends to midbrain, enters superior cerebellar peduncle, and decussates again, and enters cerebellar cortex
Concerned with proprioception

18. Lateral funiculus
Spinotectal tract fibres from same part as spinothalamic tract end in superior colliculus and reticular formation (fibres are crossed
Spinoreticular tract originates in laminae 4-8 ends in reticular formation; is important in perception of pain and other modalities originating in internal organs

19. Lateral funiculus Spino-olivary tract has uncertain role in humans
Ventrolateral fasciculus also contains descending medullary reticulospinal tract, which controls motor activities that do not require conscious effort

20. Ventral funiculus
Ventral corticospinal tract contains uncrossed fibres
Vestibulospinal tract is uncrossed pathway from the lateral vestibular nucleus of medulla; axons terminate in lamina 8
Mediates reflexes of equilibrium

21. Ventral funiculus Pontine reticulospinal tract
Medial longitudinal fasciculus (only in cord to upper cervical levels) is involved in movements of head required for equilibrium
Tectospinal tract from contralateral superior colliculus

22. Fasciculus proprius
Present in all funiculi immediately adjacent to gray matter
Contains propriospinal fibres which connect different segmental levels of gray matter
Ascend and descend variable lengths and provide functional equivalent of interneurons

23. Dorsal root entry zone Each dorsal root branches into 6-8 rootlets
Axons segregated into two divisions within each rootlet: lateral and medial
Lateral contains unmyelinated (type C) fibres and enters dorsolateral tract of Lissauer
Medial contains larger, myelinated axons, and enter white matter medial to dorsal horn

24. Vascular anatomy - Arterial
Cord is supplied by multiple radicular arteries, which form the anterior and posterior spinal artery
Radicular arteries arise from adjacent arteries at each vertebral segment
Pass through intervertebral foramina to supply nerve roots, but most do not reach the cord
Larger radicular arteries which also supply cord are called radiculomedullary arteries

25. Vascular anatomy - arterial
Anterior spinal artery originates in upper cervical region, from anterior spinal branches of vertebral artery.
6-10 anterior radicular arteries contribute to it throughout its length.
Supplies anterior two thirds of cord, via central branches and penetrating branches of pial plexus

26. Vascular anatomy – arterial territories
Cervical and first two thoracic segments of cord are supplied by radicular a. that arise from subclavian a. or branches thereof
High degree of variability
mid-dorsal region of cord (T3-T7) is supplied from radicular a. accompanying T4 or T5 root
T8 to conus supplied by artery of Adamkiewicz

27. Vascular anatomy - Adamkiewicz
Arises from left sided lumbar (segmental) artery in 80%
85% reaches cord between T9-L2; 15% between T3-T8 (in these cases it is supplemented by a radicular artery arising more inferiorly)
Has large anterior and small posterior branch
Anterior branch ascends, then gives off a small ascending branch and larger descending branch
Descending branch goes inferior (to conus) and makes an anastomotic loop with posterior spinal a.

28. Vascular anatomy – arterial
Cauda equina also supplied by branches from lumbar, iliolumbar, and lateral and median sacral a.

29. Vascular anatomy – posterior spinal artery
Paired arteries
Run along posterolateral cord
Sometimes discontinuous
Originates from verterbral artery
Has contribution from posterior radicular a.
Supplies posterior one third of cord

30. Vascular anatomy
Anterior spinal a. gives off central branches and branches to pial plexus
Central branches run in anterior median fissure and supply central cord
Pial plexus is formed from both anterior and posterior spinal a.
Give penetrating branches which supply outer cord
Some overlap between supply of central and pial branches

31. Vascular anatomy - venous
Internal and external vertebral venous plexuses
Form rings around each vertebra
Freely anastomose with each other

32. Vascular anatomy - venous
External plexus has anterior part (anterior to vertebral body) and posterior part (over posterior elements including laminae and spinous processes)
Anterior and posterior parts freely anastomose

33. Vascular anatomy - venous
Internal plexus: anterior part is on each side of PLL, posterior to vertebral body; posterior part is interior to ligamentum flavum
Vertebral body drained by basivertebral veins which enter anterior external plexus

34. Vascular anatomy - venous
Veins of cord mirror related arteries in distribution
Venules drain into anterior and posterior veins, which drain into two median longitudinal veins, and into anterolateral and posterolateral longitudinal veins lying adjacent to the nerve roots
Radicular veins join branches from internal plexus forming intervertebral veins (have valves), which exit intervertebral foramina and join their respective segmental veins