There are 31 pairs of spinal nerves that emerge from the spinal cord and transmit signals between the spinal cord and specific body regions. They are divided into cervical, thoracic, lumbar, sacral, and coccygeal nerves. The anterior rami of spinal nerves form plexuses that branch into major nerves like the brachial plexus and lumbar plexus, which provide motor and sensory innervation to the limbs and trunk. Intercostal nerves also directly innervate the chest wall.

1. NEUROSCIENCE
Topic : Spinal Nerve
By : Hermizan Halihanafiah

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Spinal Nerve
• Spinal nerve are the path of communication
between the spinal cord and the specific region
of the body

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Spinal Nerve
• 31 pairs
• Spinal nerve follows the name of corresponding
vertebra column.
• Consists cervical spinal nerve, thoracic spinal nerve,
lumbar spinal nerve, sacral spinal nerve and coccyx
spinal nerve.
• Emerge from spinal cord and through the
intervertebral foramina of vertebra.

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Spinal Nerve
• Spinal nerves:
1. 8 pairs of cervical spinal
nerves
2. 12 pairs of thoracic spinal
nerves
3. 5 pairs of lumbar spinal
nerves.
4. 5 pairs of sacral spinal nerves
5. 1 pairs of coccyx spinal
nerves.

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Spinal Nerve
• Cervical and thoracic spinal nerves arise and leave at
corresponding vertebra .
• Because the spinal cord are shorter than vertebra
column, nerve that arise from lumbar, sacral and
coccyx region of spinal cord do not leave the
vertebra column at the same level where they exit the
cord.
• The root of these spinal nerves angle inferiorly in the
vertebral canal from the end of spinal cord like wisps
of hair.

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Spinal Nerves

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• These root of this nerve, collectively called cauda
equina.
• Typical spinal nerve has 2 connection to spinal cord;
posterior / dorsal and anterior/ ventral root.
• Posterior and anterior root unite to form spinal nerve at
intervertebral foramina.
• Since posterior root contain sensory axons and
anterior root contain motor axons, spinal nerves is
classified as a mixed nerve.
• Posterior root contain posterior root ganglion which
cell bodies of sensory neuron is located.

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Spinal Nerves

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Spinal Nerves
Cervical spinal nerves
• 8 Pairs
• 1st
pair emerge between atlas and occipital bone
• The remaining emerge from the vertebral column
through intervertebral foramina.
• Spinal nerves C1 – C7 exits the vertebral canal
above their corresponding vertebra.
• Spinal nerve C8 exits vertebral canal between C7
and T1

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Cervical Spinal Nerves

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Thoracic spinal nerve
• 12 pairs
• Exits the vertebral canal below their corresponding
vertebra.
• Emerge from thoracic vertebra
• Continuous to form intercostals nerves.
Spinal Nerves

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Lumbar Spinal Nerve
• 5 pairs
• Emerge from lumbar vertebra.
• Exits the vertebral canal below their corresponding
vertebra.
Spinal Nerves

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Sacral and Coccyx Spinal Nerve
• 5 pairs
• From the spinal cord, the root of the sacral spinal
nerve enter the sacral canal (part of the vertebral
canal).
• Sacral nerves (S1-S4) exits the vertebral canal via 4
pairs of anterior and posterior sacral foramen.
• Spinal nerves S5 and Co1 exits from sacral hiatus.
Spinal Nerves

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Distribution of Spinal Nerve
Branches
• From the root, after passing the intervetebral foramen,
a spinal nerve divide into several branches.
• Theses branches are call rami (ramus) ; posterior
(dorsal) ramus and anterior (ventral) ramus.
• Posterior (dorsal) ramus serve the deep muscles and
skin of the posterior surface of the trunk.
• Anterior (ventral) ramus serve muscles and structure
of the upper and lower limbs and the skin of the lateral
and anterior surface of the trunk.

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Branches
• Spinal nerve also give off a meningeal branch, where
this branch reenter the vertebral cavity through
intervertebral foramen and supply the vertebra, vertebra
ligament and blood vessels of spinal cord and
meninges.
• Other branches from spinal nerve are the rami
communicantes ( components of ANS)
Distribution of Spinal Nerve

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Plexuses
• Axons from the anterior (ventral) rami of spinal
nerves, except for the thoracic nerves T2-T12, do not
go directly to the body structures they supply.
• They form network on both the left and right side of
the body by joining with various numbers of axons
from anterior rami of adjacent nerves.
Distribution of Spinal Nerve

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Plexuses
• Network of axons is call plexuses.
• The principle plexus:
1. Cervical plexus
2. Brachial plexus
3. Lumbar plexus
4. Sacral plexus
5. Coccygeal plexus
Distribution of Spinal Nerve

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Plexuses
• Emerging from the plexus are nerves bearing names
that are often descriptive of the general regions they
serve or the course they take.
• Each of the nerves in turn may have several branches
named for the specific structures they innervate.
Distribution of Spinal Nerve

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Plexuses
Cervical Plexus
• Formed by the roots of anterior rami of the 1st
four
cervical nerve (C1-C4), with contribution from C5.
• There is one on each side of the neck alongside the
first 4 cervical vertebrae.
• Supply the skin (sensory / cutaneous innervations)
and muscles (motor innervations) of the:
 head,
 neck
 superior part of the shoulder and chest.

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Brachial Plexus
• Form by roots of anterior rami of spinal nerves of
C5-C8 and T1.
• Extends inferiorly and laterally on either side of the
last 4 and 5 cervical vertebrae.
• Divides into roots, trunks, divisions, cords and
terminal branches (nerves).
• 5 important nerves arise from brachial plexus are
musculocutaneous, axillary, radial, ulnar and median
nerves.
• Give skin (sensory) innervations and muscles
(motor) innervations for the most of the shoulder
and upper limbs region.
Plexuses

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Lumbar Plexus
• The roots of anterior rami of spinal nerves L1-L4
form lumbar plexus.
• Minimal intermingling axons compare to brachial
plexus.
• The main nerve is a femoral (the largest) and
obturator nerves.
• Supply the skin and muscles of the:
– anterolateral abdominal wall
– external genitals (cremaster muscles, skin on scrotum, labia
majora etc)
– part of the lower limbs (adductor muscles of tight, flexor
muscles of hip and extensor muscles of knee joint)
Plexuses

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Sacral Plexus
• Form by the roots of anterior rami of spinal nerves
L4-L5 and S1-S4.
• This plexus is situated largely anterior to the sacrum
• The largest nerve in the body, sciatic nerve arise
from the sacral plexus.
• Also pudendal nerve, superior gluteal, inferior
gluteal etc.
• Supply the skin (sensory) and muscles (motor) of
the:
– Buttock
– Perineum
– Lower limbs
Plexuses

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Coccygeal Plexus
• Form from roots of anterior rami of spinal nerves S4
and S5 and the coccygeal nerves.
• Supplies a small area of skin in the coccygeal
region.
Plexuses

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Intercostal Nerves
• The anterior rami of spinal nerves T2-T12 do not
enter into the formation of plexuses and are known
as intercostal or thoracic nerves.
• These nerves directly connect to the structure they
supply in the intercostal spaces.
• After leaving its intervertebral foramen, anterior
ramus of nerve T2 innervates the intercostal
muscles of the second intercostal space and
supplies the skin of the axilla and posteromedial
aspect of the arm.

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• Nerves T3-T6 extend along the costal groove of the
ribs and then to the intercostal muscles and skin of
the anterior and lateral chest wall.
• Nerves T7-T12 supply the intercostal muscles and
abdominals muscles , along with the overlying skin.
• The posterior rami of the intercostal nerves supply
the deep back muscles and skin of the posterior
aspect of the thorax.
Intercostal Nerves

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