{{Short description|Group of tissues}} {{about|anatomical myotomes|myotomes in developmental biology and embryology|Myotome (embryology)}} {{Anchor|Myosepta|Myoseptum}} thumb|right A '''myotome''' is the group of muscles that a single spinal nerve innervates.<ref>Dorland's Illustrated Medical Dictionary 2012 Page 1226</ref> Similarly a dermatome is an area of skin that a single nerve innervates with sensory fibers. Myotomes are separated by '''myosepta''' (singular: '''myoseptum''').<ref>"Medical Definition Of MYOSEPTUM". 2018. Merriam-Webster.Com. https://www.merriam-webster.com/medical/myoseptum.</ref> In vertebrate embryonic development, a myotome is the part of a somite that develops into muscle.
==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.<ref>{{cite book|last1=Larsen|first1=William J.|title=Human embryology|date=2001|publisher=Churchill Livingstone|location=Philadelphia, Pa.|isbn=0-443-06583-7|edition=3.|page=86}}</ref> 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.<ref>[http://www.apparelyzed.com/myo-dermatomes.html Apparelyzed: ''Myotomes & Dermatomes'']</ref>
===List of myotomes=== Myotome distributions of the upper and lower extremity are as follows;<ref>{{cite book|title=Orthopaedic Physical Assessment|last=Magee|first=David. J|publisher=Elsevier|year=2006|isbn=978-1-4160-3109-3|edition=4th|location=St. Louis|pages=121–181|chapter=3}}</ref><ref>{{cite book|title=Orthopaedic Physical Assessment|last=Magee|first=David. J|publisher=Elsevier|year=2009|isbn=978-1-4160-3109-3|edition=4th|location=St. Louis|pages=467–566|chapter=9}}</ref> * C1/C2: neck flexion/extension * C3: Lateral Neck Flexion * C4: shoulder elevation * C5: Shoulder abduction * C6: Elbow flexion/Wrist Extension * C7: Elbow extension/Wrist flexion * C8: Thumb extension * T1: Finger Abduction & Adduction{{cn|date=November 2021}} * L1/L2: Hip Flexion * L3: Knee extension * L4: Ankle dorsi-flexion * L5: Great toe extension * S1: Hip extension/Ankle plantar-flexion/ankle eversion * 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.<ref>{{cite book|last=Magee|first=David. J|title=Orthopaedic Physical Assessment|year=2006|publisher=Elsevier|location=St. Louis|isbn=978-1-4160-3109-3|pages=1–63|edition=4th|chapter=1}}</ref> 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.
==References== {{Reflist}}
==Further reading== *''Neurology Textbook'', edited by Professor L. Sokolva, M.D., D.Sc. 2012, {{ISBN|9789663824260}}
==External links== * {{EmbryologyUNSW|Notes/skmus7}} * {{EmbryologyUNSW|Notes/week3_6}} * {{EmbryologyUNC|mslimb|009}}
Category:Neurology