The phrenic nerve

The phrenic nerve is the main nerve of the diaphragm. It supplies the largest part, the central part of the diaphragm. It is both a motor and a sensible nerve.

The phrenic nerve courses direct over the heart.

The phrenic nerve enters the vertebral column unexpectedly high: C3 - C5. This is caused by the fact that the diaphragm starts developing quite cranially and during embryological development migrates caudally, dragging the phrenic nerve with it. This high innervation enables patients with a vertebral cord lesion below C5 to survive, because breathing (the daiphragm is the main breathing muscle) still remains possible.