What is a Myotome?

Marco Sumayao

A myotome is most often defined as a group of muscles that are innervated by a single spinal nerve root. The tissue can involve either whole or parts of a muscle. Myotomes are responsible for a significant number of the body's motor functions. In embryology, a myotome is also defined as a tissue group that develops along the body wall in vertebrate embryos. The tissue later develops into several striated muscle groups, excluding those of the heart.

Myotomes are responsible for the movement of the diaphragm.
Myotomes are responsible for the movement of the diaphragm.

Mytome innervation results in several essential body movements, including the bending and straightening of the knees and elbows. Myotomes are also responsible for fanning and bending fingers, rotating the foot, and flexing the hip. Other motor functions involve involuntary muscle movement in organs such as bowels, diaphragms, and genitalia.

Reflex tests may be done to help diagnose myotome.
Reflex tests may be done to help diagnose myotome.

Dermatomes, skin cells supplied by a single spinal nerve root, work hand-in-hand with myotomes to produce reflexes. External stimuli register the sensation of touch on one or several dermatones, which then sends impulses to the myotomes for the appropriate bodily reaction. For example, when a finger is put into an open flame, the dermatome will send signals to the brain indicating heat and pain. The brain will respond by innverating the myotome groups responsible for jerking the finger away from the flame.

Myotomes are responsible for the bending and straightening of the elbows.
Myotomes are responsible for the bending and straightening of the elbows.

Doctors refer to myotome maps to determine several symptoms of possible nerve damage. Along with reflex tests, muscle strength tests in areas supplied by myotomes can help diagnose any areas in which nerve cell activity is either deficient or absent. These tests are often used in patients who suffered injury to the spinal cord. Alternatively, doctors can also use a patient's reported symptoms to identify damaged nerves according to their locations on the myotome map.

In cases of serious nerve damage, physical therapists can use myotome maps to aid in speedier recovery. Stimulating areas of the body that cause myotomes to react can rehabilitate weakened nerves. The results of regular myotome testing can be used to monitor the effectiveness of the therapy, allowing therapists to make appropriate adjustments in case of deficiencies.

Embryological myotomes, on the other hand, are responsible for the development of back, abdominal, and limb muscles. The myotomes develop from somites in the body wall and divide into dorsal and ventral parts, which then become the different trunk muscles respective to their location. Deficiencies in myotome development can lead to birth defects, such as quadriplegia and leptokurtic, or hunched spinal formation.

Muscle strengths tests may be performed on patients with a spinal cord injury.
Muscle strengths tests may be performed on patients with a spinal cord injury.

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Discussion Comments


You can feel how many muscles are involved in a myotome if you put one hand around your forearm and then bend your wrist back. You can feel muscles bulging in the top and bottom of your arm.

And if you're interested you can look up which myotome is related to which vertebra.

In this case, they are all joined together by the seventh cervical vertebrae.

Not that this is really all that useful to you unless you are studying in a medical profession. But, sometimes it's nice to just think about how complex your body actually is.


@KoiwiGal - I've seen those charts. They also have some that map out dermatomes. They end up looking a bit like a rainbow, just because they tend to go in layers that match the spinal vertabrae, since the myotomes and dermatomes match up to different parts of the spine.

I actually know a friend who had to learn this stuff off by heart. She was a physical therapist and they have to understand which parts of the body work together so that if one bit is injured, they can manipulate the rest to bring the injured part back to health.

It seems like it's not all that complicated when all you know about it is stretches and exercises, but taking into account myotome muscle groups and so forth, physical rehabilitation is actually quite complicated.


It's pretty cool how there are groups of muscles which are all connected by a single root nerve. I'd never really thought about it, but it makes sense to have them all transmitted through a single source if it is something that is going to need to be coordinated, like fanning your fingers.

You can actually find myotome charts of where the myotome groups are found in your body online, which can be very useful if you are studying the groups.

Particularly if you are learning about how doctors determine nerve injury by testing different areas of the body. This is like when they hit your knee with a little hammer to see if your leg pops up. If it doesn't they can tell that you might have some nerve damage, or another problem with a particular area of your body, and thus narrow down what the problem might be.

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