The humerus is the long bone in the upper arm, extending from the shoulder to the elbow. It plays a crucial role in arm movement and supports various activities, such as lifting and throwing. The humerus consists of three main parts: the head, shaft, and distal end, which connects to the elbow joint. At the proximal end, the humerus has a rounded head that fits into the glenoid cavity of the scapula, forming the shoulder joint. The bone is also important for muscle attachment, allowing for the movement of the biceps and triceps muscles, which are essential for flexing and extending the arm.