Look up information in the brachial plexus glossary.
The brachial plexus (BRAY-key-el PLEK-sis) is a network of nerves that provides movement and feeling to the shoulder, arm and hand. The nerves supporting the arm exit the spinal column high in the neck; those that support the hand and fingers exit lower in the neck.
This nerve complex is composed of four cervical nerve roots (C5-C8) and the first thoracic nerve root (T1). These roots combine to form three trunks. C5-C6 form the upper trunk, C7 continues as the middle trunk and C8-T1 form the lower trunk.
Each trunk splits into a division. Half the divisions globally supply flexor muscles (that lift and bend the arm). The others supply the extensor muscles (that straighten the arm and bring it down).