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Laboratory 9. Extensor Region of Forearm and Dorsum of Hand
Step 8. Dorsal Interosseous Muscles

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Identify the four dorsal interosseous muscles [1st] [2nd] [3rd] [4th]. Each muscle is positioned between adjacent metacarpal bones. Their tendons insert into the base of the proximal phalanx and the extensor expansion which will be examined in the next step of the dissection.

Functionally, the dorsal interosseous muscles act to abduct the fingers (i.e. index, ring, and little finger) away from an imaginary line drawn through the long axis of the middle finger. These muscles are innervated on their deep surface by branches of the ulnar nerve.

Links and References:
Grant's: 6.103-6.109
Netter (1ed.): 437, 438, 442, and 443 (2ed.): 433, 434, 438, and 439
Rohen/Yokochi: 371-373