The deltoid is a large, triangular-shaped muscle covering the shoulder joint, responsible for its rounded contour and acting as the primary abductor of the arm. It consists of three distinct sets of fibers (anterior, middle, posterior) that attach to the clavicle, acromion, and scapula, inserting into the humerus. It is essential for shoulder movement and stability, as well as a common site for injections. #fyp #f