Author: Gordana Sendić MD • Reviewer: Edwin Ocran MBChB, MSc Show
The phrenic nerve is a mixed nerve arising from the anterior rami of C3-C5 spinal nerves, which are components of the cervical plexus. It arises in the neck and descends vertically through the thorax to end on the diaphragm. The phrenic nerve is a bilateral nerve, and its left and right counterparts have some important differences in terms of course and relations with surrounding structures. The main function of the phrenic nerve is to provide the entire motor innervation to the diaphragm, which makes it a vital component in the physiology of breathing. In addition, the phrenic nerve supplies sensory innervation to the central part of the diaphragm and adjacent fascial coverings. This article will discuss the anatomy and function of the phrenic nerve. Key facts about the phrenic nerve
Origin and courseThe phrenic nerve is a deep branch of the cervical plexus arising mainly from the C4 spinal nerve, but also receives contributions from C3 and C5 spinal nerves. This fact can be remembered by the mnemonic: C3, 4, 5, keep the diaphragm alive. The phrenic nerve arises in the neck, at the upper lateral border of the scalenus anterior muscle, and descends along its anterior surface, deep to the prevertebral layer of the deep cervical fascia. The nerve runs posterior to the sternocleidomastoid muscle, the inferior belly of omohyoid muscle, the internal jugular vein, transverse cervical and suprascapular arteries. From this point on, the pathway of the left and right phrenic nerves has several differences. However, on both sides, the nerves run behind the subclavian vein and anterior to the internal thoracic artery to enter the thoracic cavity through the superior thoracic aperture. In addition, both phrenic nerves are accompanied by the pericardiacophrenic vessels along their course in the thorax. This image shows the left and right phrenic nerve in a cadaver, along with surrounding neurovascular structures.Left phrenic nerve
Right phrenic nerve
FunctionThe phrenic nerve is a mixed nerve, carrying motor, sensory and sympathetic fibers. It is the only nerve that provides motor innervation to the diaphragm, with the left and right phrenic nerves innervating their corresponding ipsilateral hemidiaphragms. Thus, the phrenic nerve stimulates the movements of the diaphragm and plays a crucial role in breathing. The phrenic nerve also provides sensory innervation to the central part of the diaphragm, as well as the pericardium, mediastinal pleura, diaphragmatic pleura and diaphragmatic peritoneum. Pro tip: To solidify your understanding of a newly learned topic, quiz yourself. Find out why anatomy quiz questions are the secret to your success! Clinical relationsPhrenic nerve damageSince the phrenic nerve provides the sole motor innervation to the diaphragm, damage of the phrenic nerve can result in paralysis or palsy of the diaphragm. Causes of phrenic nerve damage can include the following:
Bilateral damage of the phrenic nerve can be a life-threatening condition, as it results in the paralysis of the entire diaphragm. On the other hand, unilateral damage to either the left or right phrenic nerve, and the subsequent paralysis of one hemidiaphragm, can be an asymptomatic condition and an incidental finding on chest X-ray. A unilateral paralysis of one hemidiaphragm causes paradoxical movement of the diaphragm during respiration, where the affected side moves upwards during inspiration, and downwards during expiration. SourcesAll content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines. References:
Phrenic nerve: want to learn more about it? Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. What do you prefer to learn with? “I would honestly say that Kenhub cut my study time in half.” – Read more.  Which spinal plexus gives rise to the phrenic nerve?The phrenic nerve is derived from the cervical plexus and receives innervation from the C3, C4, and C5 nerve roots. It is the longest branch of the cervical plexus.
Which spinal plexus gives rise to the phrenic nerve and what organ does this nerve supply quizlet?The cervical plexus gives rise to the phrenic nerve, which innervates the diaphragm. Although the phrenic nerve is primarily a motor nerve, it has some sensory function as well.
What organ does the phrenic nerve supply?The phrenic nerve originates from the anterior rami of the C3 through C5 nerve roots and consists of motor, sensory, and sympathetic nerve fibers. It provides complete motor innervation to the diaphragm and sensation to the central tendon aspect of the diaphragm.
Where does the phrenic nerve connect to the spinal cord?Your phrenic nerve connects to the C3 to C5 cervical (neck) nerve roots of your spinal cord. The nerve: Starts at the C3 vertebral level, the part that aligns with your jaw and helps you bend and rotate your neck. Connects to the C4 and C5 vertebral levels in your neck, below the C3 vertebra.
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