The phrenic nerve is a peripheral nerve arising from the cervical plexus. It contains fibers from the C3 and C4 spinal cord segments, with contributions from C5.
Anatomy
Course
The phrenic nerve descends anterior to the anterior scalene muscle and posterior to the deep cervical fascia and the Musculus sternocleidomastoideus, then enters the superior thoracic aperture accompanied by the subclavian artery and vein. There, it initially lies anterior to the cupula of the pleura before reaching the diaphragm between the mediastinal pleura and the pericardium. It is accompanied by the pericardiacophrenic artery. Along its course, it gives off branches to the pericardium, the mediastinal pleura, and, in the abdominal cavity, to the peritoneum covering the liver, pancreas, and anterior abdominal wall.
Innervation
The phrenic nerve provides motor innervation to the diaphragm. The sensory territories supplied by the phrenic nerve include the parietal pleura, pericardium, and parts of the peritoneum.
Blood supply
The blood supply of the phrenic nerve is provided predominantly by the pericardiacophrenic artery, which arises from the internal thoracic artery.
