Back Muscles – Origin, Insertion, Action & Innervation Practice Test

Rhomboid major primarily retracts the scapula toward the spine, rotates the scapula downward (depressing the glenoid), and fixes the scapula to the thoracic wall so the shoulder can move with a stable base. Its fibers pull the medial border of the scapula medially and help hold it tight against the rib cage during arm movements. Protraction is the job of serratus anterior, elevation is done mainly by trapezius and levator scapulae, and depression is from lower trapezius or pectoralis minor, not the rhomboids.