So for example, the " flexor pollicis longus " and " flexor pollicis brevis " oppose the " extensor pollicis longus " and the " extensor pollicis brevis " in the movement of the thumb.
12.
Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the extensor pollicis brevis.
13.
Weak or absent extensors and / or abductors ( the extensor pollicis brevis tendon, the extensor pollicis longus tendon or, rarely, the abductor pollicis longus tendon ), can cause a disbalance, leading to an abnormal position of the thumb : congenital clasped thumb.
14.
The "'dorsal surface "'( " facies dorsalis; posterior surface " ) is convex, and smooth in the upper third of its extent, and covered by the Abductor pollicis longus above, and the extensor pollicis brevis muscle below.
15.
The tendons of the extensor pollicis longus and extensor pollicis brevis form what is known as the anatomical snuff box ( an indentation on the lateral aspect of the thumb at its base ) The radial artery can be palpated anteriorly at the wrist ( not in the snuffbox ).
16.
The fibres end approximately at the middle of the forearm in the form of a flat tendon, which is closely connected with that of the extensor carpi radialis longus, and accompanies it to the wrist; it passes beneath the abductor pollicis longus and extensor pollicis brevis, beneath the extensor retinaculum, and inserts into the lateral dorsal surface of the base of the third metacarpal bone, with a few fibres inserting into the medial dorsal surface of the second metacarpal bone.
