pectoralis minor, a thin triangular muscle of the upper chest wall beneath the pectoralis major. The base arises from the third, fourth, and fifth ribs on their upper outer surfaces. It inserts as a flat tendon into the coracoid process of the scapula. It functions to rotate the scapula, to draw it down and forward, and to raise the third, the fourth, and fifth ribs in forced inspiration. Compare pectoralis major, subclavius.
