The upper arm is the section of an arm from the elbow to the shoulder. The longest bone present in the upper arm is the humerus. The upper arm helps pull and lift things. The joint at the elbow allows the arm to swing 180 degrees at full extension. The round socket of the shoulder blade in which the head of the upper arm fits is called the glenoid cavity.
The fore-arm is the area between the wrist and the elbow. The bones of the fore-arm are called radio–ulna. Ulna is a longer bone than radius. The flexibility of the fore-arm depends on the three major muscles associated with the bones, the brachialis, biceps brachii and brachioradialis. The wrist is an important part of this region. It consists of 13 bones along with multiple muscles. The muscles in the fore-arm help in the rotation of the wrist.