Pectoralis major

The pectoralis major muscle 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 part 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 pectoral nerve and lateral pectoral nerve - branches of the brachial plexus; innervation for the clavicular part arises from the spinal segments C5 and C6 of the spinal cord, while for the sternocostal part from the spinal segments C7, C6 and T1 of the spinal cord.

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