Cervical plexus – part 1.

The anterior rami of nerves C1-4 form the cervical plexus. This plexus lies deep to the sternocleidomastoid (SCM) and internal jugular vein, superficial to the scalenes and levator scapula. Each of the primary rami, except C1, divide into two. C1 joins the upper branch of C2. The adjacent upper and lower branches of C2 and C3 fuse as do C3 and C4. The lower branch of C4 joins C5 and contributes to the brachial plexus.

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C1 joins the upper branch of C2.
The lower branch of C2 fuses with the upper branch of C3.
The lower branch of C3 fuses with the upper branch of C4.
The lower branch of C4 joins C5 and contributes to the brachial plexus.

cervical plexus 1

C1:
– Emerges between occipital bone and 1st cervical vertebrae.
– Often without a dorsal root.
– Consists exclusively of motor axons which innervate the subocciptal muscles, as well as the geniohyoid and infrahyoid muscles via the hypoglossal nerve (CN XII)
– Lacks sensory axons thus no dermatomes.

Deep muscular and communicating branches:

Medial muscular:

Rectus capitis lateralis – C1.
Rectus capitis anterior – C1, 2.
Longus capitis – C1, 2, 3.
Longus coli – C2, 3, 4.
Inferior root of ansa cervicalis – C2, 3.
Phrenic nerve (diaphragm) – C3, 4, 5.

Medial communicating (with):

Hypoglossal – C1, 2.
Vagus – C1, 2, 3, 4.
Sympathetic – C1, 2.

Lateral muscular:

SCM – C2,3,4.
Trapezius – C2(3).
Levator scapulae – C3, 4.
Medial scalenes – C3, 4.

Lateral communicating (with):

Accessory nerve – C2, 3, 4.

Superficial or cutaneous branches:

Ascending branches.

Lesser occipital nerve – C2 (3)
Great auricular nerve – C2-3
Transverse cervical nerve – C2-3

Descending branches.

Medial supraclavicular*
Intermediate supraclavicular*
Lateral supraclavicular*
* All arise from a common trunk formed by the 3rd and 4th ventral rami and emerge from the posterior border of the sternocleidomastoid (SCM).

Lesser occipital nerve.

Supplies skin of ear’s auricle and adjacent portion of the scalp.
Connects with posterior branch of great auricular nerve.

Great auricular nerve.

Largest ascending branch of cervical plexus.
Encircles posterior border of SCM.
Supplies skin over mastoid process, the back of the auricle, the lobule and the concha.

Transverse cutaneous nerve.

Curves around posterior border of SCM.
Supplies upper anterior skin of the neck as well as anterolaterally as far as the sternum.

Medial supraclavicular nerve.

Supplies sternoclavicular joint and skin as far as the midline and down to the level of the 2nd rib.

Intermediate supraclavicular nerve.

Cross the clavicle to supply skin over pectoralis major and deltoids, down to level of 2nd rib.

Lateral supraclavicular nerve.

Supplies skin of upper and posterior shoulder.

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