Extensor Indicis Muscle
Origin: Posterior surface of the ulna and the interosseous membrane
Insertion: Dorsal surface of the base of the middle phalanx (central slip) and distal phalanx (lateral bands) of the index digit.
Actions: Extension of the second digit
Innervation: Radial nerve (C6 C7 C8)
Blood Supply: Posterior interosseous artery from the ulnar artery
Primary Actions of the Extensor Indicis
1. Extension of the second digit at the metacarpophalangeal joint
Agonists:
- Extensor digitorum
Antagonists:
- First dorsal interossei
- First Palmar Interosseous
- First Lumbricals (hand)
- Flexor Digitorum Superficialis
- Flexor Digitorum Profundus
2. Extension of the second digit at the proximal interphalangeal joint
Agonists:
- Extensor Digitorum
- First Lumbrical
- First Dorsal Interosseous
- First Palmar Interosseous
Antagonists:
- Flexor Digitorum Profundus
- Flexor Digitorum Superficialis
3. Extension of the second digit at the distal interphalangeal joint
Agonists:
- Extensor Digitorum
- First Dorsal Interossei
- First Palmar Interossei
- First Lumbricals
Antagonists:
- Flexor Digitorum Profundus
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Secondary Actions of the Extensor Indicis:
1. Assists with adduction of the second digit at the carpometacarpal joint
Agonists:
- First Palmar Interosseous
Antagonists:
- First Dorsal Interosseous
Information about cause and effect of Extensor Indicis pain: Extensor Indicis Muscle: Hand and Finger Pain
An excellent book for those beginning the study of anatomy. Coloring helps memory retention.
For intermediary anatomy students learning skeletal and muscle structure.
For beginning and intermediary anatomy . Muscle overlays on the human body. Excellent visuals!