Which action is performed by the serratus anterior when the scapula is free to move?

• A. Abduct the scapula
• B. Elevate the thorax during forced inhalation
• C. Flex the elbow
• D. Rotate the scapula medially

Answer: (A)

Protraction (abduction) of the scapula is the action performed by the serratus anterior when the shoulder blade is free to move. This muscle wraps around the thorax from the ribs to the medial border of the scapula, so when it contracts it pulls the scapula forward and away from the spine, pressing it against the rib cage. That forward pull is the abduction you see when the scapula shifts laterally along the thoracic wall. The serratus anterior also helps upwardly rotate the scapula to allow raising the arm, but its primary movement in this context is protraction. It doesn’t elevate the thorax during forced inhalation, which involves other muscles; it doesn’t flex the elbow (elbow flexors do that), and it doesn’t medially rotate the scapula.