Art Anatomy

First Dorsal Interosseus

Pronuncation in-ter-OSS-ee-us
Derivation Between (inter) the bones (osseus) on the dorsal side of the hand.
Origin The facing surfaces of the first and second metacarpals.
Insertion Base of the proximal phalanx of the index finger.
Action Pulls the first and second metacarpals together, abducting the index finger.

There is a network of muscles between all of the metacarpals that forms the bulk of the hand. Of these muscles the first dorsal interosseus is the most distinct. This muscle forms the thumb-side wall of the hand.

It becomes prominent on the dorsal surface when the thumb is squeezed against the side of the hand.

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Next: The Thenar Muscles

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