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The phrenic nerve is a nerve that originates in the neck (C3-C5) and passes down between the lung and heart to reach the diaphragm. It is important for breathing, as it passes motor information to the diaphragm and receives sensory information from it. There are two phrenic nerves, a left and a right one. The phrenic nerve originates mainly from the 5th cervical nerve, but also receives contributions from the 4th and 3rd cervical nerves (C3-C5) in humans. Thus, the phrenic nerve receives innervation from parts of both the cervical plexus and the brachial plexus of nerves. The phrenic nerves contain motor, sensory, and sympathetic nerve fibers. These nerves provide the only motor supply to the diaphragm as well as sensation to the central tendon. In the thorax, each phrenic nerve supplies the mediastinal pleura and pericardium. ==Structure== The phrenic nerve descends obliquely with the internal jugular vein across the anterior scalene, deep to the prevertebral layer of deep cervical fascia and the transverse cervical and suprascapular arteries. On the left, the phrenic nerve crosses anterior to the first part of the subclavian artery. On the right, it lies on the anterior scalene muscle and crosses anterior to the 2nd part of the subclavian artery. On both sides, the phrenic nerve runs posterior to the subclavian vein as it enters the thorax where it runs anterior to the root of the lung and between the fibrous pericardium and mediastinal face of the parietal pleura.〔 Found in the middle mediastinum, both phrenic nerves run from C3, C4, and C5 along the anterior scalene muscle deep to the carotid sheath. * The ''right phrenic nerve'' passes over the brachiocephalic artery, posterior to the subclavian vein, and then crosses the root of the right lung anteriorly and then leaves the thorax by passing through the vena cava hiatus opening in the diaphragm at the level of T8. The right phrenic nerve passes over the right atrium. * The ''left phrenic nerve'' passes over the pericardium of the left ventricle and pierces the diaphragm separately. The pericardiacophrenic arteries and veins travel with their respective phrenic nerves. The phrenic nerve can be marked by a line connecting these two points: # 1st point can be labelled 3.5 cm at the level of the thyroid cartilage from the midsagittal plane. # 2nd point is at the medial end of the clavicle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「phrenic nerve」の詳細全文を読む スポンサード リンク
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