Phrenic nerve

Dr Owen Kang and Dr Henry Knipe et al.

The phrenic nerve is a mixed motor/sensory nerve that courses through the neck and thorax to innervate the diaphragm.

Arises from the ventral rami of the C3, C4 and C5 nerve roots, part of the cervical plexus.

In the neck, the phrenic nerve lies on the anterior surface of the anterior scalene muscle, passes over the dome of the pleura and enters the thorax posterior to the subclavian vein. The right and left phrenic nerves have a different course in the thorax but as a general rule they descend as lateral as possible whilst keeping in contact with the mediastinal pleura. 

After entering the thorax posterior to the subclavian vein it descends laterally to the left subclavian artery, arch of the aorta, left auricle and left ventricle (in contact with pericardium) before piercing the dome of the left hemidiaphragm to enter the abdominal cavity.

In contrast to the left phrenic nerve, the right is in contact with venous structures and descends laterally to the superior vena cava, right atrium and ventricle, and inferior vena cava before passing through the vena caval foramen to enter the abdominal cavity.

Within the abdominal cavity both the left and right phrenic nerves divide into three main branches - anterior, lateral and posterior. These course peripherally in a radial pattern. 

The phrenic nerve is the sole motor supply to each hemidiaphragm. It also provides sensory supply to:

  • diaphragm (except the most peripheral diaphragm, which is supplied by intercostal nerves)
  • mediastinal pleura
  • pericardium
  • central parts of diaphragmatic pleura and peritoneum
  • course anterior to the subclavian vein
  • course along the lateral border of the anterior scalene muscle
  • may pierce the anterior scalene muscle
  • accessory phrenic nerve (from C5 and C6 roots)
  • may receive additional branches from the cervical or brachial plexuses
  • may supply a branch to the subclavius muscle
Thoracic anatomy
Head and neck anatomy
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Article information

rID: 24461
Systems: Chest, Head & Neck
Section: Anatomy
Tags: cases, refs
Synonyms or Alternate Spellings:
  • Phrenic nerves
  • Left phrenic nerve
  • Right phrenic nerve

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Cases and figures

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    Figure 1: phrenic nerve
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    Figure 2: cervical plexus labelled
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