The action of the pectoralis major muscle includes primarily ____.

The pectoralis major muscle plays a crucial role in several movements of the shoulder, specifically flexion, abduction, and rotation of the arm. Understanding the muscle's anatomy and function is key to recognizing its actions:

• Flexion involves moving the arm forward and upward. The pectoralis major assists in lifting the arm in front of the body, especially when the arm starts from a position alongside the torso.

• Abduction refers to moving the arm laterally away from the body. This muscle is heavily involved when the arm is raised sideways, especially after the initial motion has begun.

• Rotation, particularly medial rotation, occurs when the arm is brought inward towards the body. The pectoralis major contributes significantly to this motion, aiding in actions like bringing the elbow back against the body.

Given that the pectoralis major is involved in all of these movements, it is accurate to say that its action includes primarily flexion, abduction, and rotation. This comprehensive involvement in various movements makes the answer correct that the action of the pectoralis major muscle encompasses all of these functions.