CHAPTER 10 Structure and Function of the Wrist and Hand Complex Central band
Dorsal digital expansion
Metacarpal
Extensor digitorum
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Lateral band
Lumbrical Figure 10.24 cont’d B Distal phalanx
Flexor digitorum profundus
Flexor digitorum superficialis
Dorsal interosseus
A
B
Figure 10.25 (A) The intrinsic plus position of the hand produced by activity of the lumbricales and interossei muscles without activity of the extrinsic finger muscles. (B) The intrinsic minus position of the hand produced by activity of the finer flexors and extensors without intrinsic muscle activity.
joint. This stretch pulls the dorsal hood distally, causing the central tendon of the extensor mechanism to relax and reducing its extensor force at the joints, allowing IP fl exion.
Intrinsic Muscles
The intrinsic muscles of the hand are small muscles that have both attachments within the hand. These muscles are responsible for the fi ne motor fi nger movements needed for intricate control and function. They are
classifi ed according to their location within the hand. The thenar muscles are located at the base of the thumb, the deep muscle group is located within the palm, and the hypothenar muscles are located at the base of the fi fth digit.
Thenar Muscles
The thenar muscle group is made up of the fl exor pollicis brevis, the abductor pollicis brevis, and the opponens pollicis. Pollicis is a Latin term referring to the thumb, thus connecting the thenar group to the thumb. The
