The dorsal aponeurosis, intrinsic, hypothenar, and thenar musculature of the hand.

The intrinsic muscles of the hand consist of seven interossei and four lumbrical muscles. With the extrinsic long extensors, the intrinsic muscles act via the dorsal aponeurosis to control finger motion. The interossei also control finger abduction and adduction, and flexion of the metacarpophalangeal joints. The lumbricals are the main extensors of the interphalangeal joints. The complex structure of the dorsal aponeurosis allows coordination and individual joint motion. The muscles of the hypothenar and thenar eminences also insert into the dorsal aponeurosis and the skeleton of the small finger and thumb, respectively, and are responsible for the specialized motion. Knowledge of the anatomy is necessary for understanding the function in treating abnormalities and trauma to the intricate structures of the hand.