Spinal Cord and Nerve Plexii

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Spinal Cord and Nerve Plexii

• By
• Nanette Lizamore
• Department Anatomy
• Section Clinical anatomy
• R4-13, BMS building
• nlizamor_at_medic.up.ac.za

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Part I Spinal cord

• 1. Organization
• - General
• - Cauda equina
• - Meninges
• 2. Structure
• Grey matter
• White matter
• 3. Blood supply
• 4. Spinal nerves
• Typical n.
• Components

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1. Organization

• Cauda equina
• Meninges

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2. Structure Grey matter

• Components Nerve cells, Processes, Neuroglia,
  Blood vessels
• Grey columns Anterior, Posterior, Transverse,
  Lateral

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Grey columns

• Anterior
• Medial group skeletal muscles of the neck and
  trunk
• Central group cervical and lumbosacral segments
  contains the phrenic, asccessory and
  lumbosacral nuclei
• Lateral group cervical and lumbosacral areas
  innervating skeletal muscles of the limbs

• Posterior
• Substantia gelatinosa concerned with pain,
  temperature and touch
• Nucleus proprius fibers from white posterior
  column associated with proprioception, 2-piont
  discrimination and vibration
• Nucleus dorsalis (Clarks column) from C8 L3/4
  proprioceptive endings in spindles
• Visceral afferent nucleus from T1 L3 receives
  visceral afferent information

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Grey columns (cont.)

• Transverse
• Contains central canal that starts in the MO,
• Inferiorly expands in the conus medullaris as the
  terminal ventricle CSF ependyma

• Lateral
• From T1L2/3
• Give rise to preganglionic
  sympathetic fibers
• Similar group in S2-4 give rise to preganglionic
  parasympathtic fibres

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2. Structure White matter

• Mixture of myelinated nerve fibers, neuroglia and
  blood vessels
• Ascending tracts
• Descending tracts
• Ascending and descending tracts with the same
  origin, course and termination Fasciculus
• Intersegmental tracts

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Ascending tracts

• Sensory, contain 1st, 2nd and 3rd order neurons
• Pathways for temperature, pain, proprioception
• Examples Spinothalamic tract (lateral
  anterior, fasciculus gracilis and cuneatus)
  Spinocerebellar tract (anterior posterior)
  Cuneocerebellat tract.
• Other Spinotectal, spinoreticular,
  spino-olivary, visceral sensory

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Descending tracts

• White matter from the supraspinal centers with
  1st, 2nd and 3rd order motor neurons
• Examples Corticospinal, reticularspinal,
  tectospinal, rubrospinal, vestibulospinal,
  olivospinal, descending autonomic

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3. Blood supply Spinal arteries

• From vertebral, posterior intercostal, lumbar,
  lateral sacral, ascending cervical, deep
  cervical, iliolumbar aa.
• Posterior spinal a. in close association to
  posterior spinal roots, but is insufficient to
  supply the spinal cord alone
• Anterior spinal a. unite to for a single artery
  on the median fissure of the spinal cord.

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Spinal arteries (cont.)

• Radicular a. reinforce the spinal arteries by
  entering through the intervertebral foramina
• Larger anterior radicular arteries A.
  radicularis magna (artery of Adamkiewicz) from
  the left an intersegmental branch of the
  descending aorta, that supplies 2/3rds of the
  spinal cord

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3. Blood supply Venous drainage

• Internal (anterior posterior) venous plexus
• External venous plexus (anterior posterior)
• Basivertebral and intervertebral veins.

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4. Typical spinal nerve

• Posterior (dorsal) root Supplies synovial joints
  of the vertebral column, deep muscles of the back
  overlying skin. Posterior root ganglia
  Sensory, unipolar with satellite cells.
• Anterior (ventral) root Supplies the remaining
  areas anterior lateral regions of the trunk
  and limbs

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Part II Nerve plexii

• 1. Cervical plexus
• 2. Brachial plexus
• 3. Lumbar plexus
• 4. Sacral plexus

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Concepts of nerve plexii

• Peripheral nerve that divide and join other
  peripheral nerves to form a network
• Plexus permits individual nerve fibers to pass
  from one peripheral nerve to another allowing
  redistribution of nerves
• Peripheral nerve Bundle of nerve fibers in a
  sheath, can be cranial or spinal
• Ganglion Collection of nerve bodies outside the
  CNS
• T2 L1 segmental innervation of skin and muscles
• Other areas nerve plexii

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1. Cervical plexus (C1 C4)

• Ansa cervicalis superior (C1) inferior (C2,3)
  radix
• Minor occipital n. (C2)
• Greater auricular n. (C2,3)
• Transverse cervical n. (C2,3)
• Supraclavicular n. (C3,4)
• Deep branches
• Phrenic n. (C3,4,5)

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1. Cervical plexus in situ
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2. Brachial plexus (C5 T1)

• Roots (C5-T1)
• Trunks Upper (C5,6), middle (C7), lower (C8,T1)
• Divisions anterior posterior
• Cords
• Lateral cords formed by the anterior divisions of
  the upper end middle trunks
• Medial cord formed by the anterior division of
  the lower trunk
• Posterior cord formed by the posterior division
  of the middle, lower upper trunks

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3. Lumbar plexus (L1 L4)

• Iliohypogastric n. (L1)
• Ilioinguinal n. (L1)
• Genitofemoral n. (L1,2)
• Lateral cutaneous n. of thigh (L2,3)
• Femoral n. (L2-L4)
• Obturator n. (L2-L4)

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4. Sacral plexus (L4 S4)

• To LL and gluteal regions
• Sciatic n.
• Superior gluteal n. (L4-S1)
• Inferior gluteal n. (L5-S1)
• Posterior cutaneous nerve of the thigh (S1-3)
• To quadriceps femoris (L4 S1)
• To obturator internus (L5,S1)
• To Pelvis
• Pudendal nerve (S2-4)
• Nn. Splanchini pelvini (S2-4)
• To levator ani coccygeus
• (S3-4)
• Perineal branch (S4)