Pectoralis Major Muscles, Gross Anatomy

Description

Across the anterior upper thorax, the pectoralis major is presented as a broad fan-shaped muscle with distinct clavicular and sternocostal heads, its fibers converging laterally toward the humerus at the lateral lip of the intertubercular sulcus. Superiorly, the clavicle forms the roof of the anterior shoulder girdle, while the sternum and costal cartilages sit medially as the major origin points for the sternocostal portion. The muscle belly overlies the ribs, and at the lateral margin the scapula and proximal humerus define the contour of the glenohumeral region. Fiber direction is clear. The proximal cervical vertebrae appear superiorly, situating the shoulder girdle beneath the neck. This anterior relationship of pectoralis major to the clavicle, sternum, and proximal humerus matters when teaching shoulder adduction and internal rotation, but it becomes concrete in surgery and sports medicine. Tendon rupture at the humeral insertion, classically in weightlifting during the eccentric phase of a bench press, is assessed by loss of the anterior axillary fold and retraction of the sternocostal head, so seeing the fiber convergence and insertion site in one frame helps readers understand the deformity. The illustration also supports discussion of anterior shoulder approaches and safe planes, where pectoralis major forms a superficial landmark over deeper neurovascular structures entering the axilla. Use this artwork in gross anatomy and kinesiology modules on the anterior thoracic wall, in orthopedic or sports medicine texts covering pectoralis major tendon tears and repair, or in preoperative patient education to explain incision placement and expected functional deficits. It also pairs well with imaging teaching files when correlating the tendon footprint on MRI or ultrasound to the humeral landmarks shown here. Anatomical accuracy verified by SciePro's Medical Advisory Board.