GLOSSARY

The cervical plexus is a network of the ventral rami of spinal nerves C1–C4, lying deep to the sternocleidomastoid, that supplies the skin of the neck, behind the ear, part of the head, and the top of the shoulder, the anterior neck muscles, and the diaphragm.

Branches

• Sensory (superficial) branches: emerge at Erb’s point on the posterior border of the sternocleidomastoid:
• Lesser occipital nerve: skin behind the ear.
• Great auricular nerve: skin over the parotid and the ear.
• Transverse cervical nerve: skin of the front of the neck.
• Supraclavicular nerves: skin over the shoulder and clavicle.
• Motor (deep) branches: the ansa cervicalis (the infrahyoid muscles) and the deep neck muscles.
• Phrenic nerve (C3–C5): the only motor nerve to the diaphragm.

The Phrenic Nerve

The well-known teaching phrase: “C3, 4, 5 keeps the diaphragm alive