spinal nerves incl brachial plexus
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Neuroanatomy:Spinal Nerves
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Spinal Nerves
Spinal nerves are paths of communicationbetween the spinal cord and the nervesinnervating specific regions of the body
(Tortora & Derrickson, 2008)
8 Cervical
12 Thoracic
5 Lumbar 31 pairs in total
5 Lumbar
1 Coccygeal
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Spinal Nerves
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Spinal Nerves
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Spinal Nerves
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Spinal Nerves
Dorsal and ventral roots unite to form a spinal
nerve at the intervertebral foramen where it
exits the vertebral canal
A spinal nerve is a mixed nerve as it contains
both sensory and motor axons
(Tortora & Derrickson, 2008)
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Spinal Nerve Structure
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Dermatomes
The whole surface area (skin) of the body is
supplied by sensory neurons
(Waugh & Grant, 2006) Each spinal nerve contains sensory neurons
that serve specific predictable segments of the
body
A Dermatome is an area of skin innervated by
the sensory fibres of a single nerve root
(Tortora & Derrickson, 2008)
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Dermatome Map
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Dermatomes C1: vertex of skull
C2: temple, forehead, occiput C3: entire neck, posterior cheek, temporal area
C4: shoulder, clavicle, and upper scapular area.
C5: deltoid area C6: lateral arm, lateral forearm, thumb, and
index finger
C7: middle finger
C8: ring and little finger, distal medial forearm T1: Proximal medial forearm and medial arm
(OBrien, 2010)
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Myotomes
Each spinal nerve contains motor neurons thatserve skeletal muscle groups
A myotome is a group of muscles primarily
innervated by the motor fibres of a single
nerve root (Tortora & Derrickson, 2008)
Upper limb myotomes (OBrien, 2010) C5shoulder abduction
C6elbow flexion
C7elbow extension
C8finger flexion
T1finger abduction.
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Spinal Nerve Plexus
Cervical Plexus formed by C1-C4
Brachial Plexus formed by C5- T1
Lumbar plexus formed by L1-L4
Sacral Plexus formed by L4,L5,S1-S4
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Cervical Plexus Formed by spinal nerves C1 to C4 (and some fibres
from C5)
Lies either side of the neck alongside the 1stfour
vertebrae
Supplies skin and muscles of head, neck, superiorshoulder and superior chest (Tortora & Derrickson,
2008)
Cranial nerve XI (innervates trapezius & SCM) runs
parallel to cervical plexus branches (Nolte, 2008)
Fibres from C3, C4 and C5 form the phrenic nerve
which supplies the diaphragm
C3,4,5 keep the diaphragm alive! (Nolte, 2008)
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Cervical Plexus
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Brachial Plexus Brachial = Upper limb, Plexus = Network
Formed by spinal nerves C5, C6, C7, C8, T1
5 nerve roots 3 trunks 6 divisions (3anterior & 3 posterior) 3 cords
5 important branches
Axillary nerve
Musculocutaneous nerve
Radial nerve
Median nerve
Ulnar nerve
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Neuroanatomy
For the 5 main branches of the brachial plexus, itis important to know the following:
The spinal segments/spinal nerve roots they originatefrom
The pathway down the upper limb
The muscles and sensory areas they innervate
Why? For entrapment neuropathies, the pattern
of sensory loss in skin and weakness in specificmuscles allows identification of the nerveinvolved and site of impingement (OBrien, 2010)
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Axillary Nerve
Arises from C5, C6
Runs down the
posterior chord of
brachial plexus
Winds around the neck
of the humerus
Supplies
- branches to deltoid &
teres minor
- cutaneous area over
deltoid
(OBrien, 2010)
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Musculocutaneous Nerve
Arises from C5, C6, C7
Runs from lateral chord of
brachial plexus, pierces
coracobrachialis, runs
between biceps and
brachialis, then down lateral
aspect of the forearm.
Supplies
coracobrachialis, biceps
and brachialis (motor)
lateral cutaneous area of
the forearm (sensory)
(OBrien, 2010)
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Radial Nerve Arises from C5, C6, C7, C8, T1
From posterior chord of brachial plexus into the auxilla
branches to the triceps, long head, lateral head and medial head.
Emerges from the auxilla between the long and medial head of the triceps
Stays in the posterior part of the arm, until above the lateral epicondoyle
where it winds anteriorly in the lower 1/3 of humerus. Gives off cutaneous branches as it winds around humerus
for the lateral posterior upper arm
down the middle of back of forearm to wrist
3 branches to the extensors of the arm
At the elbow it divides into superficial and deep Deep branch: supplies supinator and all extensor muscles in posterior aspect
of forearm
Superficial branch: supplies skin of lateral part of dorsum of hand and dorsal
surface of 3 fingers
(OBrien, 2010)
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Radial Nerve
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Ulnar Nerve
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Median Nerve
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Brachial Plexus
Other branches of the brachial plexus include: Dorsal scapular nerve
Long thoracic nerve
Nerve to subclavius
Suprascapular nerve
Lateral & Medial Pectoral nerves
Medial brachial cutaneous nerve
Medial antebrachial cutaneous nerve Upper subscapular nerve
Thoracodorsal nerve
Lower subscapular(OBrien, 2010)
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Entrapment Neuropathies
Erb Duchenne Palsy Klumpke's Palsy
Auxillary Neuropathy
Radial neuropathy
Ulnar neuropathy Median neuropathy/carpel tunnel syndrome
Bells Palsy
Saturday night palsy Thoracic outlet syndrome
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References
Tortora, G., Derrickson, B., 2008. Principles of
Anatomy and Physiology. 12thEdition. John Wiley &
Sons
Waugh, A., Grant, A, 2006. Ross and Wilson:
Anatomy and Physiology in Health and Illness. 10th
Edition. Churchill Livingstone
OBrien, M., 2010.Aids to the examination of the
peripheral nervous system. 5thEdition. Elsevier
Saunders
Nolte, J., 2008. The Human Brain: An introduction to
its functional anatomy 6th
Edition Mosby Inc
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