Muscle
Pectoralis major
Large chest muscle for bringing the arm inward
High-yield
Clavicular fibers assist shoulder flexion. Sternocostal fibers help extend an already flexed arm. Medial and lateral pectoral nerves supply the muscle.
Overview
Its clavicular and sternocostal portions converge on the proximal humerus. Both help adduct and internally rotate the arm; their different starting points also let them help move it forward or return a flexed arm backward.
Reference facts
- Origin
- Clavicular part: medial half of the clavicle; sternocostal part: sternum, upper costal cartilages and external-oblique aponeurosis
- Insertion
- Lateral lip of the humeral intertubercular groove
- Action
- Adducts and internally rotates the arm; clavicular fibers flex it, while sternocostal fibers can extend it from flexion
- Innervation
- Lateral pectoral nerve (C5–C7) and medial pectoral nerve (C8–T1)
- Blood supply
- Principally the pectoral branch of the thoracoacromial artery
Clinical correlation
Poland syndrome can include an absent or underdeveloped sternocostal portion, usually on one side. Associated hand and chest-wall differences vary, and hand involvement is not required in every case.
Frequently asked questions
What does the pectoralis major do?
Adducts and internally rotates the arm; clavicular fibers flex it, while sternocostal fibers can extend it from flexion.
What nerve innervates the pectoralis major?
Lateral pectoral nerve (C5–C7) and medial pectoral nerve (C8–T1).
Where does the pectoralis major attach?
Origin: Clavicular part: medial half of the clavicle; sternocostal part: sternum, upper costal cartilages and external-oblique aponeurosis. Insertion: Lateral lip of the humeral intertubercular groove.
What is the blood supply of the pectoralis major?
The pectoralis major is supplied by the principally the pectoral branch of the thoracoacromial artery.