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September 12, 2023

Anatomy of the Human Arm

The arm is a highly functional component of the human body, capable of large and complex movements such as throwing an object or performing fine motor skill tasks like writing with a pen. The main components of the arm are the humerus, shoulder joint, elbow joint, wrist joints and hand. Each of these features can be placed in a wide variety of positions to allow the arm to perform many different functions.

The humerus is the single bone that extends from your shoulder to your elbow (Figure 8.2.1). At its proximal end, there is a rounded area called the head of the humerus. This is the part of the humerus that articulates with your scapula to form the shoulder joint (see Chapter 9). On either side of the head is a prominent bony projection called an epicondyle, and at its top is a roughened ridge known as the lateral supracondylar ridge. These areas serve as attachment points for the powerful muscles that flex your arm at the shoulder. The lateral epicondyle also provides attachment points for the lesser tubercle and the musculocutaneous nerve (see Chapter 11).

At its distal end, the humerus tapers down to two thick knobs called condyles. The dome-shaped lateral condyle articulates with a shallow depression on the radius bone of your forearm, while the spool-shaped medial condyle fits into a deeper notch in the ulna. Immediately above the trochlea is a small knob-like region called the capitulum (literally "small head"). This region of the distal humerus interacts with the ulna bone of your lower arm.