Muscles of the Thorax

Muscles of the Thorax, Axial Skeleton, and Scapula

• The anterior muscles of the thorax that move the pectoral girdle include the pectoralis minor, serratus anterior, and subclavius.
• The posterior muscles of the thorax that move the pectoral girdle include the levator scapulae, rhomboid major, rhomboid minor, and trapezius.
• The latissimus dorsi and pectoralis major are muscles originating on the axial skeleton that move the glenohumeral joint/arm.
• The deltoid, coracobrachialis, teres major, triceps brachii (long head), biceps brachii (long head), and rotator cuff muscles are muscles originating on the scapula that move the glenohumeral joint/arm.
• The deltoid has anterior, middle, and posterior fibers that have different actions on the arm.
• The rotator cuff muscles, including the supraspinatus, infraspinatus, teres minor, and subscapularis, collectively stabilize the glenohumeral joint.
• The latissimus dorsi is also known as the "swimmer's muscle" due to its action as an agonist of arm extension.
• The pectoralis major is an agonist of arm flexion and also adducts and medially rotates the arm.
• The triceps brachii (long head) extends and adducts the arm, while the biceps brachii (long head) flexes the arm.
• The subscapularis medially rotates the arm, while the supraspinatus abducts the arm, and the infraspinatus and teres minor adduct and laterally rotate the arm.
• The origin and insertion points of each muscle are important for understanding their action and how they move the skeletal system.
• Understanding the muscles of the thorax, axial skeleton, and scapula is important for understanding the movement and function of the upper body.