The phrenic nerve is a nerve originating in the neck (C3-C5) and passes underneath the lungs and heart to reach the diaphragm. It is important to breathe, as it passes motor information to the diaphragm and receives sensory information from it. There are two phrenic nerves, the left and the right.
The phrenic nerves are primarily derived from the 4th cervical nerve, but also receive contributions from the 5th and 3rd cervical nerves (C3-C5) in humans. Thus, the phrenic nerve receives innervation from portions of both the cervical plexus and the nerve brachial plexus.
The phrenic nerve contains motor nerves, sensory, and sympathetic. This nerve provides the only motor supply to the diaphragm and also the sensation of the central tendon. In the thorax, every phrenic nerve supplies the pleural mediastinum and the pericardium.
Video Phrenic nerve
Structure
The phrenic nerve decreases tilted with the internal jugular vein along the anterior scalena, deep into the deep prevalent layer of the inner cervical fascia and the transverse cervical and transcascular arteries. On the left, the phrenic nerve crosses anteriorly to the first part of the subclavian artery. On the right, it lies in the anterior scalene muscle and crossed anteriorly to the 2nd part of the subclavian artery. On both sides, the phrenic nerve runs in the posterior of the subclavian vein as it enters the thorax where it runs anteriorly to the root of the lung and between the fibrous pericardium and the mediastinal face of the parietal pleura.
Found in the middle mediastinum, both phrenic nerves run from C3, C4, and C5 along the anterior skalena muscle deep into the carotid sheath.
- the right phrenic nerve passes through the brachialfalic artery, posterior to the subclavian vein, and then passes the anterior right lung root and then leaves the thorax by passing through the cava vein opening the diaphragmatic hiatus at T8 level. The right phrenic nerve passes through the right atrium.
- left phrenic nerve passes through the left ventricular pericardium and punctures the diaphragm separately.
The pericardiophenic and venous arteries run with their respective phrenic nerves.
The phrenic nerve can be marked by a line connecting these two points:
- The first point can be labeled 3.5 cm at the thyroid cartilage level of the midsagittal plane.
- 2 dots are at the medial end of the clavicle.
Variations
The 5th cervical nerve contribution may be derived from the phrenic accessory nerve. The phrenic nerve at the beginning of its journey approaches its origin, providing a branch that communicates to the root of C5 from the brachial plexus. The phrenic nerve at the root level of the neck just before entering the thorax is placed in front of the subclavian vein. It is usually placed posteriorly between the subclavian and arterial veins.
Most often it is a branch of the nerve to the subclavius ​​and may contain many phrenic nerve fibers. If the phrenic accessory nerve is present, it lies on the lateral main nerve and descends posteriorly and sometimes inferior to the subclavian vein. The phrenic accessory nerve is connected to the phrenic nerve in the thorax or neck root.
In the canines, the phrenic nerve arises from C5-C7 with the occasional small contribution of C4. In cats, horses, cattle, and small ruminants, the phrenic nerve arises variably from C4-C7.
Maps Phrenic nerve
Function
Both of these nerves supply motor fibers to the diaphragm and sensory fibers to the fibrous pericardium, the mediastinal pleura, and the diaphragmatic peritoneum.
Some sources describe the right phrenic nerve as innervating the gallbladder, other sources do not mention it as such.
Clinical interests
Pain arising from structures provided by the phrenic nerve is often "referred" to other somatic areas served by the C3-C5 spinal cord. For example, a subphrenic abscess under the right diaphragm may cause the patient to feel pain in the right shoulder.
Irritation of the phrenic nerve (or tissue supplied by it) leads to hiccup reflexes. Hiccups are the spasmodic contractions of the diaphragm, which draw air from the folds of the enclosed larynx.
The phrenic nerve should be identified during thoracic surgery and preserved. To confirm the identity of the phrenic nerve, gently manipulate it to obtain a dartle (diaphragmatic) response. The right phrenic nerve can be destroyed by cava vein clamps during liver transplantation. Deciding on the phrenic nerve, or phrenectomy, will paralyze half of the diaphragm. Diaphragm paralysis is best demonstrated by sonography. Breathing will become more difficult but will continue to be given another nerve is still intact.
The phrenic nerve arises from the neck (C3-C5) and inverts the diaphragm, which is much lower. Therefore, patients suffering from spinal cord injuries under the neck can still breathe effectively, although there is paralysis of the lower limbs.
Brachial plexus injury can cause paralysis to various areas of the arms, forearms, and hands depending on the disconnected nerve. The resulting palsy has been clinically treated using the phrenic nerve as a donor for neurotization of the musculocutaneous nerve and median nerve. This treatment has a high success rate (84.6%) partially for full recovery innervation to damaged nerves. Furthermore, this procedure has resulted in a function that is restored to the nerves in the brachial plexus with minimal impact on the respiratory function of the phrenic nerve. Examples where pulmonary vital capacity is diminished typically are caused by right phrenic use as a donor for neurotization whereas the use of the left phrenic nerve has not been significantly associated with a decrease in pulmonary vital capacity.
Additional images
See also
References
External links
- Anatomical figure: 19: 04-05 in Human Anatomy Online, SUNY Downstate Medical Center - "Left mediastinum side."
- Anatomical figure: 25: 03-15 in Human Anatomy Online, SUNY Downstate Medical Center - "Diagram of cervical plexus."
Source of the article : Wikipedia
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