Trigeminal nerve

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trigeminal nerves

Trigeminal nerve Trigeminal_side_small

The graphic on the right shows the rough anatomy of the Trigeminal nerve on one side of the head.

[size=12] It is called the Trigeminal because it is actually one nerve that splits into three main branches to give sensory innervation to one entire side of the face.

All the cell bodies of the nerves that go to your teeth actually lie in two masses called the Gasserian (Semilunar) ganglia.

It is this ganglion that splits into the three branches of the Trigeminal nerve. These ganglia are located under the skull, one in front of each ear.

Each nerve cell (neuron) within the ganglion sends out a long, microscopically thin extension called an axon.

[size=12] The axon extends all the way from the ganglion into its target tooth. The image immediately below shows a generalized picture of a neuron.

The cell body is the part that contains the nucleus of the cell. It is this part that actually resides in the semilunar ganglion.

The axon is the very long extension of the neuron cell that
continues into one of the nerve trunks that issue from the ganglion.

The image below shows the inferior dental plexus of the mandibular branch of the trigeminal nerve.

This is composed of thousands of axons from cell bodies located in the Gasserian ganglion. Bundles of axons leave the nerve trunk to enter each tooth.

The image below shows most of the maxillary branch of the trigeminal nerve as it branches out into the superior dental plexus.

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The image to the right is a rough representation of how individual axons combine within several layers of connective tissue sheaths to form larger nerve bundles. These in turn combine to form nerve trunks. Note that even within the nerve trunks, each individual axon retains its separate identity, thus traveling all the way from the tooth to its cell body in the ganglion on that side of the head.

The nerves in your body never exist separate from a support system composed of several types of connective tissue, and blood vessels of various sizes.

In fact, wherever you find a nerve, you will find at least one blood vessel accompanying it. Conversely, wherever you find a blood vessel, you will find at least one nerve accompanying it. Any complex of nerves and blood vessels is called a neurovascular bundle.

The blood vessels and nerves in a human body are like the roots of two intertwining trees. The source of the blood vessels is the heart, and the source of the nervous system is the brain and accompanying spinal cord. The intertwined "twigs" in the outer areas of the body combine to form larger and larger branches and "trunks" as they progress toward their respective sources.

The "nerve" inside a tooth is really a neurovascular bundle, since it is composed of connective tissue and blood vessels as well as nerve endings. Inflammation in the nerve of a tooth will often affect the chemistry and physiology of the neurovascular tissues all along the course of the nerve trunk making it difficult for anesthesia to penetrate into nerve bundles even at points relatively far removed from the actual site of the toothache.

It is easy to see why producing good anesthesia may be quite tricky if the patient puts off coming in for treatment until the inflammation has gotten out of hand.

<table id=table25 border=0><tr><td width="100%">The detail on the right is a representation of the fine anatomy of a nerve bundle as it enters into the apex (the tip) of the root of a lower front tooth.

Trigeminal nerve Nerve_detail

Note the extent to which it branches again and again inside the tooth. As the nerve bundle enters into the root, it is composed of several individual axons with accompanying blood vessels, each axon representing a separate neuron (nerve cell).

Remember that these neurons actually live well outside of the tooth itself in the Gasserian ganglion on one side of the head.

Each branch contains fewer and fewer axons until the branches become so fine that each one represents a separate axon from an individual neuron.

Upon occasion, it is very difficult to produce numbness in a particular tooth. The best way to avoid the (rare) horror show is to be treated when you first feel the pain.

Normal toothaches with moderate pain numb out just as easily as any healthy tissue. If your dentist notes something on an x-ray and recommends that you have a filling or a root canal, don't put it off until it hurts.

If you wait until you have acute pain or an abscess, even touching the tooth is painful and getting you numb may be difficult, especially if you are swollen. (Note that if the pulp is entirely dead in a tooth, and there is no pain, the tooth is simply an empty tube that happens to be filled with dead tissue, and the root canal can be done from beginning to end without any shots at all.) </TD>
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good luck