Phrenic nerve

The phrenic nerve arises from spinal nerves C3, C4 and C5. It provides motor innervation to the diaphragm and is thus responsible for the act of breathing. It also provides sensory innervation for many components of the mediastinum and pleura, as well as the upper abdomen, especially the liver and gall bladder. Pain arising from structures served by the phrenic nerve is often "referred" to other somatic regions served by spinal nerves C3-C5. For instance, angina pectoris classically is felt both in the chest and in the left arm. Likewise, a liver abscess close to the diaphragm will be felt in the right shoulder.