Radices plexus brachialis

The five roots are the five anterior primary rami of the spinal nerves, 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 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, 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, which draws the scapula laterally and is the prime mover in all forward-reaching and pushing actions.