Myotome
A myotome is the group of muscles that a single spinal nerve innervates.[1] Similarly a dermatome is an area of skin that a single nerve innervates. In vertebrate embryonic development, a myotome is the part of a somite that develops into the muscles.
Structure
The anatomical term myotome which describes the muscles served by a spinal nerve root, is also used in embryology to describe that part of the somite which develops into the muscles.[2] In anatomy the myotome is the motor equivalent of a dermatome. Myotomes are separated by myosepta.[3]
Function
Each muscle in the body is supplied by one or more levels or segments of the spinal cord and by their corresponding spinal nerves. A group of muscles innervated by the motor fibres of a single nerve root is known as a myotome.[4]
List of myotomes
Myotome distributions of the upper and lower extremity are as follows;[5][6]
- C1/C2: neck flexion/extension
- C3: neck lateral flexion
- C4: shoulder elevation
- C5: shoulder abduction
- C6: elbow flexion/wrist extension
- C7: elbow extension/wrist flexion/finger extension
- C8: finger flexion
- T1: finger abduction
- L2: hip flexion
- L3: knee extension
- L4: ankle dorsi-flexion
- L5: great toe extension
- S1: ankle plantar-flexion/ankle eversion/hip extension
- S2: knee flexion
- S3–S4: anal wink
Clinical significance
In humans myotome testing can be an integral part of neurological examination as each nerve root coming from the spinal cord supplies a specific group of muscles. Testing of myotomes, in the form of isometric resisted muscle testing, provides the clinician with information about the level in the spine where a lesion may be present.[7] During myotome testing, the clinician is looking for muscle weakness of a particular group of muscles. Results may indicate lesion to the spinal cord nerve root, or intervertebral disc herniation pressing on the spinal nerve roots.
See also
References
- ^ Dorland's Illustrated Medical Dictionary 2012 Page 1226
- ^ Larsen, William J. (2001). Human embryology (3. ed.). Philadelphia, Pa.: Churchill Livingstone. p. 86. ISBN 0-443-06583-7.
- ^ "Medical Definition Of MYOSEPTUM". 2018. Merriam-Webster.Com. https://www.merriam-webster.com/medical/myoseptum.
- ^ Apparelyzed: Myotomes & Dermatomes
- ^ Magee, David. J (2006). "3". Orthopaedic Physical Assessment (4th ed.). St. Louis: Elsevier. pp. 121–181. ISBN 978-1-4160-3109-3.
- ^ Magee, David. J (2009). "9". Orthopaedic Physical Assessment (4th ed.). St. Louis: Elsevier. pp. 467–566. ISBN 978-1-4160-3109-3.
- ^ Magee, David. J (2006). "1". Orthopaedic Physical Assessment (4th ed.). St. Louis: Elsevier. pp. 1–63. ISBN 978-1-4160-3109-3.
neurology textbook, edited by Professor L. Sokolva, M.D., D.Sc. 2012, ISBN 9789663824260