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5. Which spinal nerves participate in the cervical and the brachial plexus? Generally, how are these plexuses organized, and what structures do they serve?
5. Which spinal nerves participate in the cervical and the brachial plexus? Generally, how are these plexuses organized, and what structures do they serve?
The cervical plexus consists of contributions of ventral primary rami (VPR) of cervical spinal nerves (C1,2,3,4) that are responsible for cutaneous (sensory of skin) innervation of the neck and posterior scalp, and efferent (motor) innervation of the infrahyoid mm., diaphragm (and portions of the pericardium), and anterior & middle scalene mm.
The brachial plexus consists of contributions from the ventral primary rami (VPR) of cervical spinal nerves (C5,6,7,8,) & a thoracic spinal nerve (T1) that are responsible for innervation (afferent and efferent) of the upper limb and pectoral girdle (excluding trapezius and SCM). The brachial plexus may also include contributions from C4 & T2. The roots (ventral primary rami) and trunks of the brachial plexus may be found between the anterior and middle scalene mm.
The trunks of the brachial plexus are named according to their relative anatomical positions. The superior trunk typically consists of coalescing ventral primary rami (VPR) of C5 & C6. The middle trunk is typically the continuation of the VPR of C7. The inferior trunk typically consists of coalescing VPRs of C8 & T1.
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