Myotome

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Group of muscles innervated by the motor fibers of a single nerve root

Anatomy

A myotome is a group of muscles that are innervated by the motor fibers of a single spinal nerve root. Myotomes are essential in the study of neuroanatomy and neurology as they help in understanding the distribution of motor function in the body.

Development

During embryonic development, myotomes originate from the somites, which are segmented blocks of mesoderm located on either side of the neural tube. Each somite differentiates into three parts: the sclerotome, which forms the vertebrae and ribs; the dermatome, which forms the dermis of the skin; and the myotome, which forms the skeletal muscles.

Clinical significance

Myotomes are clinically significant in diagnosing and understanding various neurological disorders. By testing the strength and function of specific muscle groups, healthcare providers can determine the level of spinal nerve root involvement. For example, weakness in the muscles innervated by the C5 nerve root may indicate a problem at the C5 level of the spinal cord.

Myotome chart

The following is a general chart of myotomes and their corresponding spinal nerve roots:

• C1-C2: Neck flexion
• C3: Neck lateral flexion
• C4: Shoulder elevation
• C5: Shoulder abduction
• C6: Elbow flexion, wrist extension
• C7: Elbow extension, wrist flexion
• C8: Thumb extension, ulnar deviation
• T1: Finger abduction
• L2: Hip flexion
• L3: Knee extension
• L4: Ankle dorsiflexion
• L5: Great toe extension
• S1: Ankle plantarflexion
• S2: Knee flexion

Related concepts

• Dermatome (anatomy)
• Spinal cord
• Peripheral nervous system
• Motor neuron
• Reflex arc

See also

• Somite
• Sclerotome
• Dermatome (embryology)
• Neurology
• Neuroanatomy