Pectoralis Major Muscles Beneath the Skin, Lateral View

Description

Viewed from the lateral thorax with the skin rendered transparent, the pectoralis major forms a thick, fan-shaped layer over the anterior chest wall, its fascicles converging laterally toward the humerus. Superiorly and laterally, the deltoid caps the shoulder and blends with the pectoral contour at the deltopectoral groove. Along the anterior axillary fold, the inferolateral border of pectoralis major defines the transition from chest to axilla. Fiber direction is readable. A lateral perspective is where the three-dimensional bulk of pectoralis major is easiest to judge, including its relationship to the shoulder girdle and the humeral insertion that drives adduction and internal rotation. That matters in operative planning for a deltopectoral approach, where surgeons work between deltoid and pectoralis major to reach the proximal humerus or shoulder joint while protecting the cephalic vein in the deltopectoral interval. The same anatomy also underpins common injury patterns, such as tendon rupture near the humeral insertion during heavy bench press, with loss of the anterior axillary fold as a key surface clue. Use this illustration for gross anatomy teaching of the chest and shoulder, sports medicine modules on pectoralis major strain versus rupture, and orthopaedic or plastic surgery materials discussing the anterior axillary fold and the deltopectoral corridor. It also fits strength and conditioning publications that need accurate fascicle orientation for explaining force vectors across the shoulder. Anatomical accuracy verified by SciePro's Medical Advisory Board.