Page 69 - ASOP ROT Study Guide

10 . 6 Examples of Muscle Activity

We tend to think of the biceps as being the muscle most prominent during flexion of the elbow.
This is true but it also can be seen to act during supination of the forearm. It is very obvious when
using a screwdriver to secure a screw tightly. It must be turned clockwise. This action can be
carried out easily using a screwdriver in the right hand but not in the left. Supination of the forearm
is necessary and the biceps can be seen to work strongly during this action. If you turn the same
screw with the left hand, it requires pronation and this action is not so strong.

11. THE WRIST JOINT

11 . 1 General Structure

The wrist joint is a complex structure made up of many bones but for the sake of simplicity it can
be thought of as three joints next to each other. These are the joints between:

♦ The distal ends of the radius and ulna
♦ The distal radius and the first row of wrist bones (carpals)
♦ The two rows of wrist bone

The bones are held together by ligaments which run between them and across them. There are
collateral ligaments on either side arising from the radius and the ulna. No muscle bodies cross the
wrist joint. If they did so the wrist and hand would be large unwieldy structures unable to carry out
fine work in small spaces. Instead the majority of muscles controlling the wrist and hand are in the
forearm and only muscle tendons cross the wrist into the hand. Some muscles in the hand itself
control free movement of the digits.

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