Final answer:
The serratus anterior and pectoralis minor are the main muscles that protract the scapula, with the lower fibers of the trapezius also contributing to this movement.
Step-by-step explanation:
The muscles responsible for protracting (abducting) the scapula are primarily the serratus anterior, which plays a significant role in pushing the scapula forward and around the rib cage, and the pectoralis minor. When these muscles contract, they move the shoulder blade outward and forward on the thoracic wall.
This movement is crucial for actions like pushing or throwing a ball. It is worth noting that the term 'abduct' typically refers to the movement away from the body's midline, which in the context of the scapula is more specifically termed protraction.
The trapezius muscle can also contribute to this movement, particularly its lower fibers, which when contracted, tilt the scapula's medial border superiorly and laterally.