Phrenic nerve

The nerve that plays a crucial role in the control of breathing and diaphragm movement.

The phrenic nerve is a mixed nerve that carries motor, sensory, and sympathetic fibers. It primarily innervates the diaphragm, which is the main muscle involved in respiration, enabling it to contract and expand the lungs. Emerging from the cervical plexus, its origin lies in the spinal regions C3 to C5, making it essential for respiratory function.

Terminologia Anatomica

nervus phrenicus

System

Nervous system

Function

The primary function of the phrenic nerve is to stimulate the diaphragm to contract. During inhalation, the diaphragm moves downwards, creating a negative pressure in the thoracic cavity, which allows air to flow into the lungs. When the diaphragm relaxes during exhalation, air is expelled from the lungs. Additionally, the phrenic nerve provides sensory information from the diaphragm and the pleura, enhancing the body's ability to regulate breathing efficiently. This nerve's impact extends beyond mere respiration, as it plays a role in maintaining the overall stability of the thoracic cavity dimensions, which is vital during physical activity and various body positions.

Location

The phrenic nerve emerges from the neck, specifically from the cervical spinal nerves C3, C4, and C5, which are located in the upper spine. From its origin, the nerve descends vertically through the neck, traveling anterior to the anterior scalene muscle and then between the two layers of the pleura surrounding the lungs. It passes into the thoracic cavity, where it ultimately reaches the diaphragm, branching into several terminal fibers that innervate the muscle. This unique pathway underscores the important anatomical relationship between the nerve and key structures in the neck and chest.

Did You Know?

The phrase 'C3, C4, C5 keep the diaphragm alive' is commonly used to remember the spinal levels that contribute to the phrenic nerve.
Damage to the phrenic nerve can result in respiratory difficulties such as paralysis of the diaphragm, potentially requiring mechanical ventilation.
The phrenic nerve can also be involved in referred pain syndromes, where issues in the diaphragm may manifest as pain in the shoulder or neck.