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The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used, for instance, for pointing. The extensors are situated within 6 separate compartments.
It contains tendons of the flexor digitorum superficialis and the flexor digitorum profundus, but not the flexor pollicis longus. [2] The sheath which surrounds the flexor digitorum extends downward about halfway along the metacarpal bones, where it ends in blind diverticula around the tendons to the index, middle, and ring fingers.
In human anatomy, the annular ligaments of the fingers, often referred to as A pulleys, are the annular part of the fibrous sheathes of the fingers.Four or five such annular pulleys, together with three cruciate pulleys, form a fibro-osseous tunnel on the palmar aspect of the hand through which passes the deep and superficial flexor tendons.
On the back of the hand, the ED tendons diverge to follow the fingers and the EI tendon joins the ulnar side of one of the ED tendons along the back of the index finger. The EDM takes a similar course as the EI except it follows the ED tendon along the little finger. The ECU crosses from the lateral to the medial side of the forearm.
Passing through the first tendon compartment, it inserts to the base of the first metacarpal bone. A part of the tendon reaches the trapezium, while another fuses with the tendons of the extensor pollicis brevis and the abductor pollicis brevis. Except for abducting the hand, it flexes the hand towards the palm and abducts it radially.
These tendons, along with those of flexor digitorum profundus, are enclosed by a common flexor sheath. The tendons attach to the anterior margins on the bases of the intermediate phalanges of the four fingers. These tendons have a split (Camper's Chiasm) at the end of them through which the tendons of flexor digitorum profundus pass.
As the tendons cross the interphalangeal joints, they furnish them with dorsal ligaments. The tendon to the index finger is accompanied by the tendon of extensor indicis, which lies on its ulnar side. On the back of the hand, the tendons to the middle, ring, and little fingers are connected by two obliquely placed bands, one from the third ...
The other three palmar interossei originate on the side of the metacarpal facing the hand's midline (ray of long finger); [4] the second is attached to the medial side of the index finger; the third to the lateral side of the ring finger; and the fourth to the lateral side of the little finger. The tendons of these three muscles pass posterior ...