Which muscle elevates the scapula and facilitates head movement backward and side to side?

The correct answer highlights the role of the superior trapezius muscles, which are integral in elevating the scapula as well as facilitating movement of the head. The trapezius is a large muscle that extends from the back of the neck and the spine down to the shoulder. When the superior part of the trapezius contracts, it enables the shoulders to lift, which is critical during movements that involve shrugging or raising the arms overhead.

Moreover, the superior trapezius aids in the movement of the head. It helps in tilting the head backward (extension) and allows for lateral flexion, which permits the head to move side to side. This dual function emphasizes the importance of the superior trapezius in upper body mobility.

The other muscle groups mentioned have different primary functions that do not include scapular elevation or head movement in the same capacity as the trapezius. Deltoids are primarily responsible for arm abduction, brachialis is involved in elbow flexion, and the coracobrachialis assists with shoulder flexion, but none of these muscles contribute significantly to the elevation of the scapula or the specific head movements described.