Pectoralis Major

Musculus pectoralis major

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The pectoralis major is the large, fan-shaped prime mover of the chest, adducting and internally rotating the humerus and driving all horizontal and incline pressing. Its clavicular (upper) head flexes the shoulder while the sternocostal head extends it from flexion, so incline and flat/decline pressing emphasize different fibers. It is the central target of the bench press, dips, and chest fly variations, and its tendon is a common rupture site under heavy eccentric bench loads.

Actions

Shoulder flexion (clavicular head), Shoulder extension from flexed position (sternocostal head), Shoulder horizontal adduction, Shoulder adduction, Shoulder internal (medial) rotation

Origin

Clavicular head: anterior surface of the medial half of the clavicle. Sternocostal head: anterior surface of the sternum and the superior six costal cartilages, plus the aponeurosis of the external oblique

Insertion

Lateral lip of the bicipital (intertubercular) groove of the humerus, on the crest of the greater tubercle, via a flat bilaminar tendon

Innervation

Lateral pectoral nerve (clavicular head, C5-C6) and medial pectoral nerve (sternocostal head, C7-T1)

Blood supply

Pectoral branch of the thoracoacromial trunk; lateral thoracic artery; perforating branches of the internal thoracic artery

Heads

Clavicular head, Sternocostal head, Abdominal head

Wikipedia ↗

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