Page 200 - Clinical Anatomy

ECA3 7/18/06 6:45 PM Page 185

The bones and joints of the upper limb 185

3◊◊On either side the joints are reinforced by the collateral ligaments, which
are lax in extension and taut in flexion of the joint.

The muscles acting on the hand
The long flexors of the fingers are:
1◊◊flexor digitorum profundus, inserted into the base of the four distal pha-
langes;
2◊◊flexor digitorum superficialis, inserted into the sides of the four middle
phalanges.
The profundus tendon pierces that of superficialis over the proximal
phalanx.
The profundus flexes the distal phalanx, superficialis the middle
phalanx; acting together they flex the fingers and the wrist (Fig. 136).
The long extensors of the fingers are:
• extensor digitorum longus, reinforced by
• extensor indicis } which join the appropriate tendons of
• extensor digiti minimi extensor digitorum longus on their medial
sides.
The tendons of extensor digitorum terminate in each finger by
an aponeurotic extensor expansion which covers the dorsum of the proxi-
mal phalanx and the sides of its base. It then attaches by a central slip into
the base of the middle phalanx and by two lateral slips to the distal phalanx
(Fig. 136).
The margins of the extensor expansion are reinforced by the tendons of
the intrinsic muscles of the fingers:
1◊◊the dorsal and palmar interossei, arising from the sides and the fronts of
the metacarpals respectively;
2◊◊the lumbricals, which arise from the four profundus tendons and run on
the radial side of the m/p joints to join the extensor expansion.

Fig. 136◊The tendons of a finger. (a) Lateral view. (b) Posterior view.