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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.
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.
Flexor digitorum profundus lies deep to the superficialis, but it attaches more distally. Therefore, profundus's tendons go through the tendons of superficialis, and end up attaching to the distal phalanx. For this reason profundus is also called the perforating muscle. [2] The lumbricals of the hand arise from the radial side of its tendons. [2]
The absence of the tendon of the extensor digitorum communis to the little finger is associated with the thicker type 3r juncturae tendinum in the fourth intermetacarpal space. [3] Hirai et al. reported type 1 junturae tendinum between the extensor digiti minimi and the extensor digitorum communis to the ring finger in 6% of the specimens. [1]
Joints of the hand, X-ray Interphalangeal ligaments and phalanges. Right hand. Deep dissection. Posterior (dorsal) view. The PIP joint exhibits great lateral stability. Its transverse diameter is greater than its antero-posterior diameter and its thick collateral ligaments are tight in all positions during flexion, contrary to those in the metacarpophalangeal joint.
Fingers do not contain muscles (other than arrector pili). The muscles that move the finger joints are in the palm and forearm. The long tendons that deliver motion from the forearm muscles may be observed to move under the skin at the wrist and on the back of the hand. Muscles of the fingers can be subdivided into extrinsic and intrinsic muscles.
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 .
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.