DEPICTING THE ARM BACK VIEW

DEPICTING THE ARM BACK VIEW

Bones Much of the overall shape of the arm in the back view is determined by the under­ lying skeletal structure, just as with the front view. The inner and outer epicondyle (0 and (E), are again identifiable, even under layers of muscle. And from this view, the olecranon, or elbow (F), also is evident. 

Muscles Muscles work in opposing pairs: Flexors (see page 30, figures 2 and 3) pull and extensors extend, moving in the opposite direction. When a flexor or extensor muscle becomes active, its opposite becomes passive. From the back view, when the hand is pronate (illustrated in figures 2 and 3 above), extensor groups are the most prominent muscles. On the upper arm, the tricep is the most visible extensor. On the lower arm, extensor carpi radialis langus, extensor carpi ulnaris, and extensor digitorum, which all originate on the outer epicondyle, are evident. 

Drawing Tips The tricep has three heads (the long and outer heads are shown here; the medial head lies beneath). All share a common tendon: a flattened form on the back of the upper arm.