Page 74 - ASOP ROT Study Guide

Movement - the ability of the thumb to touch the tips of the other digits is due to the saddle shape
of the joint between the base of the first metacarpal and the trapezium (one of the carpal bones).
This joint allows movement in two directions. The metacarpal can be extended away from the
palm and also brought across the palm. It can also be adducted towards the index finger and
abducted to stand straight up in the air. The fine control of the thumb is due to the intrinsic
muscles in the thenar eminence at its base. These are innervated by the median nerve.

Sensation - the radial half of the hand is supplied by the median nerve. The sensory supply is very
well developed and consequently the thumb, index and middle fingers can accurately determine the
size, texture, temperature and shape of objects.