he three chapters in Part III describe the structures and functions of the four joints of the upper extremity. The upper extremities allow a person to perform personal care, work, and recreation activities with relative ease. Chapter 8 introduces the shoulder complex, which is formed by articulations involv- ing the sternum, clavicle, ribs, scapula, and humerus. Chapter 9 studies the elbow and forearm and how the structures associated with the humerus, ulna, and radius infl uence the function of the elbow and forearm. Chapter 10 explains the structures and func- tions of the wrist and hand.
Although the components of the upper extremity are pre- sented in separate chapters, it is imperative to understand that without the contribution of each section of the upper extremity, the function of the entire arm can be impaired. Opening and closing the hand around an object is of little use if the elbow and shoulder cannot function to reach for the object. The proximal shoulder complex must also provide a stable base on which the distal segments can move and manipulate objects. Part III lays the foundation for understanding how each component of the arm contributes to the total function of the extremity. These chapters explain how the shoulder complex provides the large range of motion needed to reach for a hat on a shelf and how the hand provides the intrinsic fi ne control needed to thread a needle.
