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Phrenic nerve

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Nerve: Phrenic nerve
Gray806
The phrenic nerve and its relations with the vagus nerve. (Phrenic labeled at upper left.)
Gray804
Plan of the cervical plexus. (Phrenic labeled at bottom right.)
Latin nervus phrenicus
Gray's subject #210 928
Innervates
From C3-C5 of cervical plexus
To
MeSH [1]

The phrenic nerve arises from the third, fourth, and fifth cervical spinal nerves (C3-C5) in humans. It arises from the fifth, sixth and seventh cervical spinal nerves (C5-7) in most domestic animals.

FunctionEdit

The phrenic nerve is made up mostly of motor nerve fibres for producing contractions of the diaphragm. In addition, it provides sensory innervation for many components of the mediastinum and pleura, as well as the upper abdomen, especially the liver and gall bladder.

PathEdit

Both phrenic nerves run from C3, C4 and C5 along the anterior scalene muscle deep to the carotid sheath.

Both these nerves supply motor fibres to the diaphragm and sensory fibres to the fibrous pericardium, mediastinal pleura and diaphragmatic peritoneum.

The pericardiacophrenic artery and vein(s) travel with the phrenic nerve.

Clinical relevanceEdit

Pain arising from structures served by the phrenic nerve is often "referred" to other somatic regions served by spinal nerves C3-C5. For example, a subphrenic abscess (beneath the diaphragm) might cause a patient to feel pain in the right shoulder.

Irritation of the phrenic nerve (or the tissues supplied by it) leads to the hiccup reflex. A hiccup is a spasmodic contraction of the diaphram, which pulls air against the closed folds of the larynx.

The phrenic nerve must be identified during thoracic surgery and preserved. It passes anterior to the hilum of the corresponding lung, and therefore can be identified easily. Severing the phrenic nerve will paralyse that half of the diaphragm. Breathing will be made more difficult but will continue provided the other nerve is intact.

Additional imagesEdit

External linkEdit


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