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Neuroanatomy   spinal cord
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Neuroanatomy spinal cord

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  • 1. SPINAL CORD PROF DR NASARUDDIN ABDUL AZIZ Management & Science University [email_address]
  • 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
  • 5.  
  • 6.  
  • 7.  
  • 8.  
  • 9.  
  • 10.  
  • 11. Structure Of The Spinal Cord
  • 12.  
  • 13.  
  • 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, T º, touch)
      • proprioceptive (from muscles & joints)
  • 24. Organization
    • Ascending pathway that reach consciousness consists of 3 neurons:
      • 1 st -order neuron
      • 2 nd -order neuron
      • 3 rd -order neuron
    • Branch to reticular formation (wakefulness)
    • Branch to motor neurons (reflex activity)
  • 25.
    • Lateral spinothalamic tract
      • pain & T º
    • 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
  • 26.  
  • 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
    • 1 st -order neurons
    • Pain conducted by δ A-type fibres & C-type fibres
    • 2 nd -order neurons
      • decussate to the opposite side
      • ends in thalamus (ventral posterolateral nucleus
    • 3 rd -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 2 nd -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
  • 34.  
  • 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
  • 37.  
  • 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
  • 39.  
  • 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
  • 43.  
  • 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
  • 45.  
  • 46.  
  • 47.  
  • 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
  • 49.  
  • 50.  
  • 51.  
  • 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