Location

The clavicular head of the pectoralis major takes its origin from the anterior surface of the medial half of the clavicle. The sternocostal head takes its origin from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle.

The muscle fibres then converge and inserted into the lateral lip of the intertubucular groove of the humerus

Action

Clavicular head : flexes the humerus
Sternocostal head : extends the humerus

As a whole, the pectoralis major adducts and laterally rotate the humerus. It also draws the scapula anteriorly and inferiorly.

Innervation

• lateral and medial pectoral nerves
• the clavicular head is innervated by nerves from C5 and C6
• the sternocostal head is innervated by nerves from C7, C8 and T1

Blood supply

pectoral branch of the thoracoacromial trunk