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Myotome

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Myotome

A myotome is the group of muscles that a single spinal nerve root 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.

Contents

  • Structure 1
  • Function 2
    • List of myotomes 2.1
  • Clinical significance 3
  • See also 4
  • References 5
  • External links 6

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.

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.[3]

List of myotomes

Myotome distributions of the upper and lower extremity are as follows;[4][5]

  • 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
  • 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
  • S3S4: 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.[6] 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

  1. ^ Dorland's Illustrated Medical Dictionary 2012 Page 1226
  2. ^ Larsen, William J. (2001). Human embryology (3. ed. ed.). Philadelphia, Pa.: Churchill Livingstone. p. 86.  
  3. ^ Myotomes & DermatomesApparelyzed:
  4. ^ Magee, David. J (2006). "3". Orthopaedic Physocal Assessment (4th ed.). St. Louis: Elsevier. pp. 121–181.  
  5. ^ Magee, David. J (2009). "9". Orthopaedic Physocal Assessment (4th ed.). St. Louis: Elsevier. pp. 467–566.  
  6. ^ Magee, David. J (2006). "1". Orthopaedic Physical Assessment (4th ed.). St. Louis: Elsevier. pp. 1–63.  

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