<prompt> what is the root value of phrenic nerve?C3,4,5C2,3,4C4,5,6C5,6,7  <response>: Phrenic nerve C3,C4,C5- It descends in front of scalenus anterior muscle . Descends down to enters thorax where it lies between subclan veinin front and subclan aery lies behind it . Fuher it descends in front of hilum of the lungs whereas vagus nerve descends behind the hilum of lungs It is mixed nerve sensory and motor.both motor and sensory to diaphragm 