DEPICTING THE ARM FRONT VIEW

DEPICTING THE ARM FRONT VIEW

Bones The underlying skeletal structure determines much of the overall shape of the arm (figure 1). Several elements of this substructure, such as the inner epicandyle (E), act as visual landmarks that are identifiable even under layers of muscle (figure 2) and skin (figure 3). 

Muscles The upper and lower portions of the arm each consist of three major muscle masses. The bicep and brachialis of the upper arm bend the lower arm, the tricep (see page 31) straightens it, and the deltaid raises the entire arm. In the lower arm, the flexars (flexor carpi radiales, palmerus longus, and flexor carpi ulnaris) bend the palm and clench the fingers; the extensors on the back of the arm (see page 31) straighten the palm and open the fingers; and the supinators (brachioradialis, see page 31), attached to the outer epicandyle (0, figure 1) on the outside arm, rotate the hand outward. A fourth, smaller muscle, the Praetorian teres, rotates the palm inward.   

Drawing Tips The bicep does not extend across the full width of the upper arm. The del­ toid inserts in between the brachialis and the bicep.