Pectoral Region and Axilla

The muscles of the pectoral region and axilla are innervated by spinal nerves from C5-T1 (the brachial plexus).

Subclavius:

• Originates on the first rib/costal cartilage
• Inserts on the inferior surface of the clavicle
• Depresses the lateral end of the clavicle

Pectoralis minor:

• Originates on the third, fourth, and fifth ribs
• Inserts on the coracoid process of the scapula
• Depresses and stabilizes the scapula, and elevates the ribs during deep inspiration.
• Pectoralis minor overlies key clinically important neurovascular structures.

Pectoralis major (clavicular head) & Pectoralis major (sternocostal head)

• Originates on the medial half of the clavicle, the sternum, and first 6 ribs.
• Inserts on the lateral lip of the intertubercular groove of the humerus
• Flexes, adducts, and medially rotates the humerus.
• Comprises the bulk of the anterior thoracic wall.
• Cephalic vein traverses superficially along superolateral border of pectoralis major.

Serratus anterior:

• Originates on the lateral aspect of the first 8 ribs and wraps posteriorly.
• Inserts on the medial border of the scapula.
• Stabilizes, abducts, and protracts the scapula.

Clinical Correlation:

• "Winged" scapula, in which the medial border projects posteriorly, occurs if the long thoracic nerve is damaged.