Anatomy of spinal cord

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Anatomy of spinal cord

  1. 1. SPINAL CORD PROF DR NASARUDDIN ABDUL AZIZ Management & Science University [email_address]
  2. 2. OBJECTIVES <ul><li>describe the external structure of the spinal cord, </li></ul><ul><li>draw and describe the internal structure of the spinal cord, </li></ul><ul><li>draw and describe the ascending and descending tracts within the spinal cord, </li></ul><ul><li>describe the meninges surrounding the spinal cord, </li></ul><ul><li>describe the blood supply of the spinal cord, </li></ul><ul><li>explain the clinical correlations of & applications related to the spinal cord </li></ul>
  3. 3. Gross Appearance <ul><li>Cylindrical in shape </li></ul><ul><li>Foramen magnum  L1/L2 (adult) </li></ul><ul><li>L3 (newborn) </li></ul><ul><li>Occupies upper ⅔ of vertebral canal </li></ul><ul><li>Surrounded by 3 layers of meniges: </li></ul><ul><ul><li>dura mater </li></ul></ul><ul><ul><li>arachnoid mater </li></ul></ul><ul><ul><li>pia mater </li></ul></ul><ul><li>CSF in subarachnoid space </li></ul>
  4. 4. <ul><li>Enlargements: cervical & lumbar </li></ul><ul><li>Conus medullaris </li></ul><ul><li>Filum termniale </li></ul><ul><li>Anterior median fissure </li></ul><ul><li>Posterior median sulcus </li></ul><ul><li>31 pairs of spinal nerves attached to it by the anterior roots & posterior roots </li></ul>
  5. 11. Structure Of The Spinal Cord
  6. 14. Gray Matter <ul><li>H-shaped pillar with anterior & posterior gray horns </li></ul><ul><li>United by gray commissure containing the central canal </li></ul><ul><li>Lateral gray column (horn) present in thoracic & upper lumbar segments </li></ul><ul><li>Amount of gray matter related to the amount of muscle innervated </li></ul><ul><li>Consists of nerve cells, neuroglia, blood vessels </li></ul>
  7. 15. <ul><li>Nerve cells in the anterior gray columns </li></ul><ul><li>Large & multipolar </li></ul><ul><li>Axons pass out in the anterior nerve roots as α -efferents </li></ul><ul><li>Smaller nerve cells are multipolar </li></ul><ul><li>Axons pass out in anterior roots as ɣ-efferents </li></ul>
  8. 16. <ul><li>Nerve cells in the posterior gray columns </li></ul><ul><li>4 nerve cell groups </li></ul><ul><li>Substantia gelatinosa </li></ul><ul><ul><li>situated at the apex </li></ul></ul><ul><ul><li>throughout the length of spinal cord </li></ul></ul><ul><ul><li>composed mainly of Golgi Type II neurons </li></ul></ul><ul><ul><li>receives afferent fibres concerning with pain, temperature & touch from posterior root </li></ul></ul>
  9. 17. <ul><li>Nucleus proprius </li></ul><ul><ul><li>anterior to substantia gelatinosa </li></ul></ul><ul><ul><li>present throughout the whole length of spinal cord </li></ul></ul><ul><ul><li>main bulk of cells in posterior gray column </li></ul></ul><ul><ul><li>receives fibers from posterior white column that are assoc with proprioception, 2-point discrimination & vibration </li></ul></ul>
  10. 18. <ul><li>Nucleus dorsalis (Clark’s column) </li></ul><ul><ul><li>base of posterior column </li></ul></ul><ul><ul><li>C8 – L3 / L4 </li></ul></ul><ul><ul><li>associated with proprioceptive endings (neuromuscular spindles & tendon spindles) </li></ul></ul><ul><li>Visceral afferent nucleus </li></ul><ul><ul><li>lateral to nucleus dorsalis </li></ul></ul><ul><ul><li>T1 – L3 </li></ul></ul><ul><ul><li>receives visceral afferent info </li></ul></ul>
  11. 19. <ul><li>Nerve cells in the lateral gray columns </li></ul><ul><li>Formed by the intermediolateral group of cells </li></ul><ul><li>T1 – L2 / L3 </li></ul><ul><li>Cells give rise to preganglionic sympathetic fibres </li></ul><ul><li>In S2, S3, S4; they give rise to preganglionic parasympathetic fibres </li></ul>
  12. 20. <ul><li>The gray commissure & central canal </li></ul><ul><ul><li>connects the gray on each side </li></ul></ul><ul><ul><li>central canal in the centre </li></ul></ul><ul><ul><li>posterior gray commissure </li></ul></ul><ul><ul><li>anterior gray commissure </li></ul></ul><ul><ul><li>central canal present throughout </li></ul></ul><ul><ul><li>superiorly continuous with the central canal of medulla oblongata </li></ul></ul><ul><ul><li>inferiorly, expands as terminal ventricle </li></ul></ul><ul><ul><li>terminates within the root of filum terminale </li></ul></ul>
  13. 21. White Matter <ul><li>Divided into </li></ul><ul><ul><li>anterior white column </li></ul></ul><ul><ul><li>lateral white column </li></ul></ul><ul><ul><li>posterior white column </li></ul></ul><ul><li>Consists of nerve fibres, neuroglia, blood vessels </li></ul><ul><li>White due to myelinated fibres </li></ul>
  14. 22. Tracts <ul><li>Ascending </li></ul><ul><li>Descending </li></ul><ul><li>Intersegmental </li></ul>
  15. 23. Ascending Tracts <ul><li>Fibres that ascend from spinal cord to higher centres </li></ul><ul><li>Conduct afferent information which may or may not reach consciousness </li></ul><ul><li>Information may be </li></ul><ul><ul><li>exteroceptive (pain, T º, touch) </li></ul></ul><ul><ul><li>proprioceptive (from muscles & joints) </li></ul></ul>
  16. 24. Organization <ul><li>Ascending pathway that reach consciousness consists of 3 neurons: </li></ul><ul><ul><li>1 st -order neuron </li></ul></ul><ul><ul><li>2 nd -order neuron </li></ul></ul><ul><ul><li>3 rd -order neuron </li></ul></ul><ul><li>Branch to reticular formation (wakefulness) </li></ul><ul><li>Branch to motor neurons (reflex activity) </li></ul>
  17. 25. <ul><li>Lateral spinothalamic tract </li></ul><ul><ul><li>pain & T º </li></ul></ul><ul><li>Anterior spinothalamic tract </li></ul><ul><ul><li>light (crude) touch & pressure </li></ul></ul><ul><li>Fasciculus cuneatus </li></ul><ul><li>Fasciculus gracilis </li></ul><ul><ul><li>discriminatory touch, vibration, info from muscles & joints </li></ul></ul><ul><li>Anterior spinocerebellar tract </li></ul><ul><li>Posterior spinocerebellar tract </li></ul><ul><ul><li>unconscious info from muscles, joints, skin, subcut </li></ul></ul>
  18. 27. <ul><li>Spinotectal tract </li></ul><ul><ul><li>spinovisual reflexes </li></ul></ul><ul><li>Spinoreticular tract </li></ul><ul><ul><li>info from muscles, joints & skin to reticular formation </li></ul></ul><ul><li>Spino-olivary tract </li></ul><ul><ul><li>indirect pathway to cerebellum </li></ul></ul>
  19. 28. Lateral spinothalamic tract <ul><li>Pain & temp pathways </li></ul><ul><li>1 st -order neurons </li></ul><ul><li>Pain conducted by δ A-type fibres & C-type fibres </li></ul><ul><li>2 nd -order neurons </li></ul><ul><ul><li>decussate to the opposite side </li></ul></ul><ul><ul><li>ends in thalamus (ventral posterolateral nucleus </li></ul></ul><ul><li>3 rd -order neurons </li></ul><ul><ul><li>ends in sensory area in postcentral gyrus </li></ul></ul>
  20. 29. Anterior spinothalamic tracts <ul><li>Light (crude) touch & pressure pathways </li></ul>
  21. 30. Posterior white column <ul><li>Discriminative touch, vibratory sense, conscious muscle joint sense (conscious proprioception) </li></ul>
  22. 31. Posterior spinocerebellar tract <ul><li>Muscle joint sense pathways to cerebellum </li></ul><ul><li>Unconscious proprioception </li></ul><ul><li>Muscle joint info from muscle spindles, GTO, joint receptors of the trunk & lower limbs </li></ul><ul><li>Info is used by the cerebellum in the coordination of movements & maintenance of posture </li></ul>
  23. 32. Anterior spinocerebellar tract <ul><li>Majority of 2 nd -order neurons cross to the opposite side </li></ul><ul><li>Enter cerebellum through superior cerebellar peduncle </li></ul><ul><li>Info from trunk, upper & lower limbs </li></ul><ul><li>Also carries info from skin & subcut tissue </li></ul>
  24. 33. Descending Tracts <ul><li>Lower motor neurons </li></ul><ul><li>Upper motor neurons </li></ul><ul><li>Corticospinal tracts </li></ul><ul><ul><li>concerned with voluntary, discrete, skilled movements </li></ul></ul>
  25. 35. <ul><li>Reticulospinal tract </li></ul><ul><ul><li>facilitates or inhibits voluntary movement or reflex activity </li></ul></ul><ul><li>Tectospinal tract </li></ul><ul><ul><li>reflex postural movements in response to visual stimuli </li></ul></ul><ul><li>Rubrospinal tract </li></ul><ul><ul><li>facilitates activity of flexor muscles & inhibits activity of extensor muscles </li></ul></ul><ul><li>Vestibulospinal tract </li></ul><ul><ul><li>facilitates extensor muscles, inhibits flexor muscles </li></ul></ul>
  26. 36. Meninges <ul><li>Dura mater </li></ul><ul><li>Arachnoid mater </li></ul><ul><li>Pia mater </li></ul>
  27. 38. Dura mater <ul><li>Dense, strong fibrous membrane </li></ul><ul><li>Encloses the spinal cord & cauda equina </li></ul><ul><li>Continuous above with meningeal layer of dura covering the brain </li></ul><ul><li>Ends at the level of S2 </li></ul><ul><li>Separated from wall of vertebral canal by the extradural space </li></ul><ul><li>Contains loose areolar tissue & internal vertebral venous space </li></ul>
  28. 40. Arachnoid mater <ul><li>Delicate impermeable membrane </li></ul><ul><li>Lies between pia and dura mater </li></ul><ul><li>Separated from pia mater by subarachnoid space </li></ul><ul><li>Continuous above with arachnoid mater covering the brain </li></ul><ul><li>Ends on filum terminale at level of S2 </li></ul>
  29. 41. Pia mater <ul><li>Vascular membrane </li></ul><ul><li>Closely covers spinal cord </li></ul><ul><li>Thickened on either side between nerve roots to form the ligamentum denticulatum </li></ul>
  30. 42. Blood supply <ul><li>Arteries of the spinal cord </li></ul><ul><li>Anterior spinal artery </li></ul><ul><li>Posterior spinal artery </li></ul><ul><li>Segmental spinal arteries </li></ul>
  31. 44. <ul><li>Anterior spinal artery </li></ul><ul><li>Formed by the union of 2 arteries </li></ul><ul><li>From vertebral artery </li></ul><ul><li>Supply anterior ⅔ of spinal cord </li></ul><ul><li>Posterior spinal arteries </li></ul><ul><li>Arise from vertebral artery or posterior inferior cerebellar arteries (PICA) </li></ul><ul><li>Descend close to the posterior roots </li></ul><ul><li>Supply posterior ⅓ of spinal cord </li></ul>
  32. 48. <ul><li>Segmental spinal arteries </li></ul><ul><li>Branches of arteries outside the vertebral column </li></ul><ul><li>Gives off the anterior & posterior radicular arteries </li></ul><ul><li>Great anterior medullary artery of Adamkiewicz </li></ul><ul><li>Arise from lateral intercostal artery or lumbar artery at any level from T8 – L3 </li></ul>
  33. 52. Clinical correlations <ul><li>Spinal shock </li></ul><ul><li>Follows acute severe damage to the spinal cord </li></ul><ul><li>All cord functions below the level of the lesion become depressed or lost </li></ul><ul><li>Sensory impairment and flaccid paralysis occur </li></ul><ul><li>Segmental spinal reflexes are depressed </li></ul><ul><li>Persists for less than 24 hours (may be as long as 1 – 4 weeks) </li></ul>
  34. 53. <ul><li>Poliomyelitis </li></ul><ul><li>Acute viral infection of the neurones of anterior gray column </li></ul><ul><li>Motor nuclei of cranial nerves </li></ul><ul><li>Death of motor neurone cells -> paralysis & wasting of muscles </li></ul><ul><li>Muscles of lower limb more often affected </li></ul>
  35. 54. <ul><li>Spinal anaesthesia </li></ul><ul><li>Extradural anaesthesia </li></ul>

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