Page 61 - ASOP ROT Study Guide

The upper limb is suspended from the axial skeleton (the spine, skull, rib cage and breastbone) by
groups of large muscles. The only joint holding the upper limb to the rest of the skeleton is the
joint between the collar bone (clavicle) and the breast bone (sternum). The shoulder girdle from
which the rest of the upper limb hangs includes the clavicle (collar bone) and the scapula (shoulder
blade).
The shoulder joint itself includes the articulation between the scapula and the thorax (chest) and
between the scapula and humerus. The elbow joint is formed by the distal humerus and the two
forearm bones; the radius and the ulna. The wrist joint is formed by the end of the radius and the
seven small wrist bones. The end of the ulna only contributes to the wrist joint via a cartilage disc.
In the hand many small joints controlled by many individual tendons make both precise movements
and a powerful grip possible. However, the hand would be much less useful without the thumb and
its ability to touch the tips of each of the other digits.
7.3 Shape
You can see in Figure 25 that the humerus and forearm bones are not in a straight line. A slight
angle (in the coronal plane) occurs at the elbow. This is called the carrying angle and enables the
forearm to swing past the pelvis. In women the average angle is a little greater than in men, to
allow the arm to swing clear of their wider pelvis.

8. THE SHOULDER GIRDLE

8 . 1 Function
Unlike the pelvic girdle, the shoulder girdle is a light and mobile structure and has the ability to
move on the chest wall under the control of several large muscles. Its functions are:
♦ to suspend the arm from the axial skeleton
♦ to participate in moving the arm and so position the hand in space
8 . 2 Structure
Shoulder girdle (illustrated below) is made up of the clavicle and scapula. These two bones
are joined together where the lateral end of the clavicle meets the acromion process of the
scapula. You can feel this bony process and the indentation of the joint at the point of your
own shoulder. The shoulder girdle is suspended from the chest wall by a joint between the sternum
and the medial end of the clavicle. This joint is the only bony attachment of the shoulder girdle to
the rest of the skeleton.

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