Corpus: Extensor indicis muscle
Synonyms: extensor indicis, extensor indicis proprius muscle
Definition
The extensor indicis muscle belongs to the deep layer of the extensors of the forearm.
Anatomy
Its origin is on the posterior surface of the ulna and the interosseous membrane of the forearm, below the origin of the extensor pollicis longus muscle. Its tendon passes through the 4th tendon compartment of the extensor retinaculum and attaches, along with the tendon of the extensor digitorum muscle, to the dorsal aponeurosis of the index finger (Digit II).
Variant
In some instances, an independent muscle belly for the tendon to the second finger can be observed. Additionally, the tendon to the fifth finger may be absent. Double tendons for individual fingers have also been documented.
Innervation
The innervation is provided by the deep branch of the radial nerve, with fibers from segments C7 and C8.
Function
The extensor indicis muscle causes extension (straightening) of the index finger.