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Spinal Cord and Nerve
Plexii
By
DR. T
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1. Organization
- General
- Cauda equina
- Meninges2. Structure
Grey matter
White matter
3. Blood supply
4. Spinal nerves
- Typical n.
- Components
Part I: Spinal cord
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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: cervicaland lumbosacral
segments & contains thephrenic, asccessory and
lumbosacral nuclei
Lateral group: cervical
and lumbosacral areasinnervating skeletalmuscles of the limbs
Posterior:
Substantia gelatinosa:concerned with pain,temperature and touch
Nucleus proprius: fibersfrom white posteriorcolumn associated withproprioception, 2-piontdiscrimination andvibration
Nucleus dorsalis (Clarkscolumn) from C8 L3/4proprioceptive endings inspindles
Visceral afferent nucleusfrom T1 L3 receivesvisceral 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
preganglionicsympathetic fibers
Similar group in S2-4give rise topreganglionicparasympathtic 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 isinsufficient 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 otherperipheral nerves to form a network
Plexus permits individual nerve fibers to passfrom 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 theCNS
T2 L1 segmental innervation of skin andmuscles
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 ofthe upper end middle
trunks Medial cord formed by
the anterior division ofthe lower trunk
Posterior cord formed bythe posterior division of
the middle, lower & uppertrunks
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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 ofthe 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)