8.1. Introduction
- General features:
- Formed by anterior primary rami of C1–C4
- Located behind the sternocleidomastoid muscle and anterior to the scalenus medius and levator scapulae muscles
- Anastomotic loops that are related to the spinal accessory (XI) and hypoglossal nerves (XII)
- Cutaneous branches of the cervical plexus:
- Greater occipital nerve (C2) innervates the skin of the posterior scalp
- Lesser occipital nerve (C2); innervates the skin of the mastoid process and lateral head; mastoid portion overlaps VII sensory innervation
- Greater auricular nerve (C2–C3):
- Innervates skin of the lower cheek over the mandible (overlaps V2, V3; auriculotemporal and buccinator nerve of V)
- Upper neck below the external ear
- Cutaneous nerves of the transverse colli (cutaneous cervical nerves; C2–C3); innervates primarily the anterior neck
- Supraclavicular nerves (C3–C4); innervates the skin above the clavicular fossa
Innervation of the Muscular Branches of the Cervical Plexus
- Ansa hypoglossi:
- A loop formed by C1 (courses with the hypoglossal nerve) and joins fibers from C2 and C3 roots that innervate: sternohyoid, omohyoid, sternothyroid, thyrohyoid, geniohyoid
- Muscles synergistic in head flexion (hyoid group)
- Phrenic nerve (C3–C5); C4 the dominant root
- Branches to the middle scalene and levator scapulae (C3–C4):
- Middle scalene: lateral flexion of the neck
- Levator scapulae muscles: rotation of the scapula
- Branches to the spinal accessory nerve
- Cranial nerve XI which supplies:
- Sternocleidomastoid (C2)
- Trapezius (C3–C4)
- Courses with XI
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