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Definition of nerve plexus and its anatomy.
Hey everyone! This is Nicole from Kenhub, and in this tutorial, we will be answering the question, what is a nerve plexus?
In order to best describe what a nerve plexus is, let's first look at some definitions around the phrase nerve plexus beginning with the word plexus itself. So, what does the word plexus mean? Plexus is the Latin name term for "braid" which is a reference to the intricately woven or web-like network of intersecting nerves that together make up a nerve plexus.
So now that we know what a plexus is, the next question we want to ask is how is a nerve plexus formed? A nerve plexus is formed by the intersecting subdivisions of the anterior or ventral rami of spinal nerves. Note that not all spinal nerve ventral rami form plexuses. For example, the ventral rami of the spinal nerves arising between the level of the second to twelfth thoracic vertebrae or T2 to T12 do not contribute to a nerve plexus.
There are four major pairs of nerve plexuses – the cervical plexus, the brachial plexus, the lumbosacral plexus which is the collective term for the lumbar plexus and the sacral plexus and finally, the coccygeal plexus. Let's now take a closer look at each nerve plexus.
So, the first nerve plexus we're going to look at today is the cervical plexus, and the cervical plexus is formed from the ventral rami of spinal nerves from the first through fourth cervical vertebra or C1 to C4. The sensory fibers from this plexus supply the posterior head, the anterior neck and the superior aspect of the shoulders. It also supplies motor fibers to many of the muscles of the neck.
As we descend further, the next plexus encountered is the brachial plexus. The brachial plexus is formed by the ventral rami of spinal nerves arising from the level of the fifth cervical vertebra to the first thoracic vertebra – C5 to T1. The brachial plexus is primarily responsible for supplying the upper limb though it also supplies the diaphragm, the superficial scapular muscles and some of the structures of the superior thorax.
The superior portion of the lumbosacral plexus is the lumbar plexus, and the lumbar plexus is formed from the ventral rami of the first four lumbar spinal nerves or L1 to L4. The lumbar plexus supplies the inferior anterior abdominal wall as well as the thigh and the leg. After the lumbar plexus comes the sacral plexus which is formed from the ventral rami of the fourth and fifth lumbar spinal nerves L4 and L5 as well as from the ventral rami of the first four sacral spinal nerves or S1 to S4. The sacral plexus predominantly supplies the pelvis and it gives off two prominent nerves – the sciatic nerve and the pudendal nerve.
Finally, the coccygeal plexus is formed from the ventral rami of spinal nerves of the fourth and fifth sacral nerves S4 and S5 as well as the coccygeal nerves. The coccygeal plexus supplies the coccygeus muscle, part of the levator ani muscle and the sacrococcygeal joint. This plexus also gives rise to the anococcygeal nerve, and the anococcygeal nerve supplies the skin around the coccyx.