The brachial plexus is a somatic nerve plexus formed by intercommunications among the ventral rami of the lower four cervical nerves ( C 5 - C 8) and the first thoracic nerve (T 1). The plexus is responsible for the motor innervation to all of the muscles of the upper limbwith the exception of the trapezius and levator scapula. It supplies all of the cutaneous innervation of the upper limb with the exception of the area of the axilla (armpit) (supplied by the intercostobrachial nerve), an area just above the point of the shoulder (supplied by supraclavicular nerves) and the dorsal scapular area which is supplied by cutaneous branches of dorsal rami. The brachial plexus communicates with the sympathetic trunk by gray rami communicates that join all the roots of the plexus and are derived from the middle and inferior cervical sympathetic ganglia and the first thoracic sympathetic ganglion.
