The shoulder girdle moves through a combination of elevation, depression, protraction (abduction), retraction (adduction), upward rotation, and downward rotation.
Here's a breakdown of these movements:
- Elevation: The shoulder girdle moves superiorly, such as shrugging the shoulders.
- Depression: The shoulder girdle moves inferiorly, such as when relaxing after shrugging.
- Protraction (Abduction): The scapula slides anteriorly and laterally along the rib cage, effectively moving the shoulder forward (e.g., reaching forward).
- Retraction (Adduction): The scapula slides posteriorly and medially along the rib cage, effectively moving the shoulder backward (e.g., squeezing the shoulder blades together).
- Upward Rotation: The inferior angle of the scapula rotates laterally and superiorly. This movement is important for raising the arm overhead.
- Downward Rotation: The inferior angle of the scapula rotates medially and inferiorly, returning from the upwardly rotated position. This movement is important for bringing the arm back down from an overhead position.
These movements are achieved through coordinated actions of several muscles, including the trapezius, rhomboids, serratus anterior, pectoralis minor, and levator scapulae.
