The root value of the long thoracic nerve is?
a. The long thoracic nerve (external respiratory nerve of Bell; posterior thoracic nerve) supplies the Serratus anterior.
b. This nerve characteristically arises by three roots from the fifth, sixth, and seventh cervical nerves (C5-C7) but the root from C7 may be absent. The roots from C5 and C6 pierce the Scalenusmedius, while the C7 root passes in front of the muscle.