The pectoralis major is a paired thick, fan-shaped muscle of the thoracic wall that provides movements of the upper limb. It is the most superficial muscle in the pectoral region, and it covers the anterior surface of the thorax, stretching between the shoulder and sternum. The pectoralis major muscle has three parts:

• Clavicular part
• Sternocostal part
• Abdominal part

Origin: clavicular part - anterior surface of the medial half of the clavicle; sternocostal part - anterior surface of the sternum, upper six costal cartilages; abdominal part - anterior layer of the rectus abdominis muscle sheath.

Insertion: crest of the greater tubercle of the humerus.

Action: all parts - adduction and medial (internal) rotation of the upper arm; clavicular part - flexion of the arm; sternocostal part - extension of the arm.

Innervation: medial and lateral pectoral nerves - branches of the brachial plexus; innervation for the clavicular part arises from the spinal segments C5 and C6, while for the sternocostal part from the C7, C6 and T1.

Blood supply: branches of the thoracoacromial and internal thoracic arteries.