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Origin: Common extensor tendon from lateral epicondyle of humerus, and deep antebrachial fascia.

Insertion: By four tendons, each penetrating a membranous expansion of the dorsum of the second to fifth digits and dividing over the proximal phalanx into a medial and two lateral bands. The medial band inserts into the base of the middle phalanx while the lateral bands reunite over the middle phalanx and insert into the base of the distal phalanx.

Innervation: Radial, C6, 7, 8

Action: Extends the MCP joints and, in conjunction with the lumbricals and interossei, extends the IP joints of the second through fifth digits. Assists in abduction of the index, ring, and little fingers; and assists in extension and abduction of the wrist

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Extrinic Extensors | Extrinsics Flexors | Extrinsic Muscles | Instinsic Muscles | Musclel Arrangement | Help | Hand Kinesiology

Lorie Richards and Janice Loudon, University of Kansas Medical Center, School of Allied Health,
Occupational and Physical Therapy Education, October 1997