「 Wikipedia 」には以下のような解説が見られる。
「 The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves (C3-C5) in humans.[1] 」
以下は頚神経叢の起始や枝を簡単に表した図になる。
「 日本人体解剖学 (上巻) 」には以下のような解説が見られる。
「第3～第5頚神経から起こり、前斜角筋の前面からその内側縁に沿って下行し、胸鎖関節の後ろで鎖骨下動脈と鎖骨下静脈との間を通って胸腔内に入り、ついで縦隔胸膜と心膜との間で肺根の前を心膜横隔動脈とともに横隔膜に達し、放線状に分布する。 」
横隔神経には以下の2枝が見られる。
以下は「 日本人体解剖学 (上巻) 」の解説の一部になる。
「 右横隔神経から出るものは大静脈孔を通り、また左横隔神経からでるものは食道裂孔を通って横隔膜下面に出て、交感神経の枝とともに横隔神経叢をつくる。
横隔神経は、頚部で交感神経幹あるいは中頚神経と交通して交感神経線維をうけるほか、肝臓および副腎にいく分枝を出す。 」
以下は「 Wikipedia 」の解説文となる。
「 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 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves (C3-C5) in humans.[1] 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.[1]
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 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.
Variation
The contribution of the 5th cervical nerve may stem from an accessory phrenic nerve. Phrenic nerve in its early course close to its origin, was giving a communicating branch to C5 root of brachial plexus. The phrenic nerve at the level of root of neck just before entering the thorax was placed in front of the subclavian vein. Usually it is placed posterior in between subclavian vein and artery.[2]
Most often it is a branch of the nerve to the subclavius and may contain numerous phrenic nerve fibers. If the accessory phrenic nerve is present, it lies lateral to the main nerve and descends posterior and occasionally inferior to the subclavian vein. The accessory phrenic nerve connects to the phrenic nerve in the thorax or the root of the neck.[1]
In canines the phrenic nerve arises from C5-C7 with occasional small contributions from C4.[3] In the cat, horse, ox, and small ruminant the phrenic nerve arises variably from C4-C7.
Function
Both of these nerves supply motor fibers to the diaphragm and sensory fibers to the fibrous pericardium, mediastinal pleura, and diaphragmatic peritoneum.
Some sources describe the right phrenic nerve as innervating the gallbladder, other sources make no such mention.[4]」
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