What are the 4 plexuses of spinal nerves?

This musical mnemonic helps students remember which spinal nerves contribute to which nerve plexuses.

One, five! Five, one!
Twelve, four! Four, four!
One, five! Five, one!
Twelve, four! Four, four!

C1, C5! C5, T1!
T12, L4! L4, S4!
C1, C5! C5, T1!
T12, L4! L4, S4!

Cervical plexus! Brachial plexus!
Lumbar plexus! Sacral plexus!
Cervical plexus! Brachial plexus!
Lumbar plexus! Sacral plexus!
Amen!

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• (with melody play-back)

A plexus is a bundle of intersecting nerves, blood vessels, or lymphatic vessels in the human body. These bundles typically originate from the same anatomical area and serve specific areas of the body. Bundles of nerves that form a plexus communicate information to your brain about pain, temperature, and pressure.

These nerve plexuses also send messages from the brain to the muscles, allowing for movement to occur. A plexus serves as an area where spinal nerves come together, are sorted, and then travel to their respective areas of the body.

Plexus Locations

Blood vessels that form a plexus are found throughout the body where arteries and veins branch into smaller capillaries. These plexuses serve to ensure that blood flow is undisturbed if one vessel becomes blocked or injured.

This is also true for lymphatic plexuses. These groups of lymph vessels allow for the undisturbed movement of lymph in your body.

Nerve bundles forming a plexus are also located throughout your body. There are two major groups of nerve plexuses in the body—the spinal plexus and the autonomic plexus. There are five distinct plexuses in each of these major groups of nerves. They are named based on the location or function of the plexus.

Spinal Plexus

Five plexuses originate from the spinal cord in your body. The five plexuses include:

• Cervical plexus: The cervical plexus originates from cervical level one through four and innervates the back of your head and the upper cervical muscles.
• Brachial plexus: The brachial plexus originates from cervical levels five through eight and thoracic level one. This plexus of nerves innervates your chest, shoulder, and arms. The three major nerves of your arm originate from the brachial plexus, the are the median nerve, the ulnar nerve, and the radial nerve.
• Lumbar plexus: The lumbar plexus originates from lumbar levels one through four and innervates muscles and skin in your hip and thigh. Two major nerves originate via the lumbar plexus—the femoral nerve and the obturator nerve. These nerves supply motor information to your hip and thigh muscles and communicate sensory information from your thighs and hips to your brain. Branches of the lumbar plexus also innervate areas of your pelvic girdle and genital area.
• Sacral plexus: The sacral plexus originates from lumbar level four through sacral level four. Your sciatic nerve comes from this plexus and serves the muscles and skin of the back of your thighs, lower legs, and feet. Other nerves that originate from the sacral plexus innervate your gluteal and piriformis muscles of your hips.
• Coccygeal plexus: This plexus serves a small area near your tailbone.

Autonomic Plexus

The five autonomic plexuses include:

• Celiac plexus (also known as the solar plexus): This plexus sits behind your stomach and innervates organs of your abdomen.
• Auerbach's plexus: This plexus innervates your gut and functions as part of your digestive system.
• Pharyngeal plexus: The pharyngeal plexus originates from cranial nerve IX through XI and innervates muscles and skin of the front of your neck. This plexus of nerves aids in the swallowing mechanism.
• Cardiac plexus: The cardiac plexus provides innervation to your heart muscle.
• Meissner's plexus: This plexus of nerves innervates your intestinal wall and works with Auberbach's plexus to aid with digestion.

Function of a Plexus

So why even have a plexus of nerves? Why not just have each individual nerve leave the spinal cord and run directly to a muscle?

A plexus of nerves can be thought of as an electrical junction box. Various nerves come together, are sorted, and then travel on to their respective muscle or anatomical structure to communicate signals to and from your brain.

This has a protective effect; an injury to one nerve may only affect specific parts of a muscle while leaving other parts intact that are innervated by a different nerve in the same plexus.

Injury to a Plexus

An injury to a plexus of nerves may cause various symptoms including pain, weakness, numbness and tingling, or paralysis of muscles. The most common plexus to be injured is the brachial plexus of the arm. This may occur due to tension and overstretching, compression, or tearing of the nerves in the plexus.

An injury to a plexus may be minor, or it may be a severe problem. Minor plexus injuries result in mild symptoms that are temporary. One example of a plexus injury is a "stinger." These often occur during sports participation where the brachial plexus in the upper arm is disrupted, often from a sudden pulling of your arm.

When a stinger happens, mild tingling and burning pain in your neck, shoulder, and arm may occur. Symptoms last for a few seconds, and then quickly subside.

Other plexus injuries may be more severe. If a forceful trauma to your arm causes significant tensioning of the brachial plexus, more permanent damage may result, leading to persistent tingling, numbness, weakness, or paralysis of the muscles in your arm or leg. This typically occurs as the result of significant trauma such as a car accident, sports injury, or fall.

Treatment of Plexus Injuries

If you have suffered any injury, visit your physician right away. They can assess your condition and make recommendations for proper treatment. Diagnosis of an injury to a plexus typically involves a clinical examination followed by a test called electromyography (EMG).

During an EMG test, small needles are placed along your arm or leg where the nerves of a plexus travel. Then, tiny electrical signals are passed between the needles. The speed at which those signals travel is measured and compared to accepted normal values.

A slowing of the electrical signal indicates that a specific nerve is damaged. Once that nerve of a specific plexus is identified, treatment can be properly directed. Sometimes other diagnostic tests, like a magnetic resonance imaging (MRI) or computerized tomography (CT scan), are performed to look for damage to a nerve plexus.

A minor injury to a plexus usually requires no treatment at all. Symptoms tend to be mild and temporary, and usually go away with the passage of time.

Some plexus injuries may require more intensive treatments for you to recover. Treatment for a ruptured nerve may involve surgery to repair the damage. Surgery may involve a nerve transfer, neurolysis (freeing nerves from scar tissue), or a nerve graft.

These surgeries are considered most effective when performed within six months of the injury, so time is of the essence. Keep in mind that nerve tissue grows very slowly, so your recovery timeline after surgery to a plexus of nerves may be measured in years.

After a nerve plexus injury, you may benefit from working with a physical therapist or occupational therapist. They can assess your condition and prescribe specific treatments to maintain muscle function and joint range of motion.

A Word From Verywell

Your body is a complex series of muscles, bones, tendons, and nerves. When nerves exit your spinal canal, they are sorted and organized in a plexus. This plexus serves to keep nerve signals organized and to create a system where your nerves are protected from injury. A disruption of one nerve may be mitigated by its neighboring nerves.

A plexus injury may cause numbness, tingling, or loss of movement. Severe plexus injuries may require the care of a qualified physician to help you fully recover.