Editing Brachial plexus (section)

===Roots===
The five '''roots''' are the five [[anterior ramus of spinal nerve|anterior primary rami]] of the [[spinal nerve]]s, after they have given off their segmental supply to the muscles of the [[neck]].
The brachial plexus emerges at five different levels: C5, C6, C7, C8, and T1. C5 and C6 merge to establish the upper trunk, C7 continuously forms the middle trunk, and C8 and T1 merge to establish the lower trunk.
Prefixed or postfixed formations in some cases involve C4 or T2, respectively.
The [[dorsal scapular nerve]] comes from the superior trunk<ref name="Anatomy and Physiology"/> and innervates the [[rhomboid muscles]] which retract and downwardly rotate the scapula. The subclavian nerve originates in both C5 and C6 and innervates the [[Subclavius muscle|subclavius]], a muscle that involves lifting the first ribs during respiration. The long thoracic nerve arises from C5, C6, and C7. This nerve innervates the [[Serratus anterior muscle|serratus anterior]], which draws the scapula laterally and is the prime mover in all forward-reaching and pushing actions.