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



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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



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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

Spinal Nerves Incl Brachial Plexus

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