M. extensor digitorum communis longus
It arises on the lateral epicondyle of the humerus by two heads: the lateral one arises by a thin tendon in common with the m.extensor carpi ulnaris with fibers proximally fused. The internal one arises by a short tendon in common with proximally fused fibers of the m. extensor carpi radialis. It divides distally in two heads: the external head inserts with a long and thin tendon on the metacarpal V, at the same point of insertion of the m. abductor brevis dorsalis digiti V; the internal one inserts by a thin tendon on the proximal region of the metacarpal IV, between the m. extensor brevis superficialis digiti IV and the m. extensor brevis medius digiti IV (Pristimantis bogotensis).