The arm, or upper limb, is a complex appendage primarily responsible for manipulation and interaction with the immediate environment. Structurally, it comprises several segments, including the scapula, humerus, radius, and ulna, which articulate through major joints to provide a wide range of motion. Functionally, it acts as a system for locomotion within a confined space and for executing fine motor tasks. The biomechanics of the arm involve coordinated action from multiple muscle groups, tendons, and ligaments. This intricate system allows for grasping, reaching, pushing, and pulling, facilitating nearly every form of environmental interaction required for physical sustenance and communication.