Phrenic nerve
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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.
The right phrenic nerve passes over the right brachiocephalic artery, the subclavian vein, and the superior vena cava and then crosses the root of the right lung and then leaves the thorax by passing through the opening in the diaphragm at the level of T10. The right phrenic nerve passes over the right atrium. The left phrenic nerve passes over the left ventricle and peirces the diaphragm separately.
Both these nerves supply motor fibres to the diaphragm and sensory fibres to the fibrous pericardium, mediastinal pleura and diaphragmatic peritoneum.
External link
- 1918 Grey's anatomy article that includes the phrenic nerve (http://www.bartleby.com/107/210.html)