Pectoralis Major, Gross Anatomy

Description

Arising from the medial clavicle, the sternum and adjacent costal cartilages, and a distinct abdominal slip from the anterior rectus sheath, the left pectoralis major forms a broad anterior chest wall sheet that converges laterally toward the proximal humerus. Superior fibers run inferolaterally from the clavicle, while the sternocostal and abdominal fibers sweep superolaterally, creating the familiar axillary fold at the muscle’s lateral border. Deep to the muscle mass, the sternum sits medially, ribs and costal cartilages curve laterally and inferiorly, and the clavicle spans superolaterally toward the shoulder; a portion of scapula and proximal humerus anchors the shoulder girdle relationship. The abdominal portion is smaller but unmistakable. Understanding the abdominal and lower sternocostal fibers matters when teaching the layered anatomy of the anterior thorax and when planning incisions that traverse the inframammary region. Tears at the humeral insertion and rupture of the musculotendinous junction are common in bench press injuries, and the pattern of fiber orientation helps explain the typical contour deformity and loss of adduction and internal rotation strength. Surgeons also use the pectoralis major as a myocutaneous flap in chest wall reconstruction and head and neck coverage, so seeing its broad origin and lateral convergence clarifies arc of rotation and donor-site anatomy. Use this artwork for gross anatomy lab teaching of the thoracic wall and shoulder, for sports medicine and orthopedics texts discussing pectoralis major rupture, and for operative atlases covering pectoralis major flap elevation and anterior chest approaches. It also fits patient-facing education on chest muscle injuries when paired with clinical photos or MRI. Anatomical accuracy verified by SciePro's Medical Advisory Board.