Which muscle is responsible for elevating, depressing, retracting, and rotating the scapula?

The trapezius muscle is primarily responsible for elevating, depressing, retracting, and rotating the scapula. This large, flat muscle extends from the base of the skull, down the spine, and out to the shoulder blades. Its various parts (upper, middle, and lower fibers) have specific roles: the upper fibers elevate the scapula (as seen when shrugging the shoulders), the middle fibers retract it (pulling the shoulder blades together), and the lower fibers assist in depressing it (lowering the shoulder blades). Additionally, the trapezius plays a crucial role in the rotation of the scapula, which is necessary for fully raising the arms overhead. This versatility in movement makes the trapezius an essential muscle for shoulder and upper back function.