Pectoralis Major muscle is large muscle of upper chest, fanning across the chest from the shoulder to the breastbone. The two pectoralis major muscles, commonly referred to as the ‘pecs,’ are the muscles that create the bulk of the chest.
pectoralis major muscle consist of clavicular part and sternal part.
- Clavicular head – originates from the anterior surface of the medial clavicle.
- Sternocostal head – originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle
The upper and lower fibers of pectoralis major insert to the crest of greater tubercle of the humerus. Upper fibers are more anterior and caudal on the crest, while posterior fibers twist on themselves and are more posterior and cranial than the upper fibers.
Nerve supply to pectoralis major comes from brachial plexus.
Nerve of the upper fibers: Lateral pectoral nerve, C5,6,7.
Nerves to the lower fibers: Lateral and medial pectoral nerve, C6, 7,8, T1.
pectoral branch of the thoracoacromial trunk
Its major actions are adduction, or depression, of the arm (in opposition to the action of the deltoideus muscle) and rotation of the arm forward about the axis of the body.
When the raised arms are fixed (as in mountain climbing), it assists the latissimus dorsi and teres major muscles in pulling the trunk up.
|Origins||Clavicular part: anterior surface of medial half of clavicle|
Sternocostal part: anterior surface of sternum, Costal cartilages of ribs 1-6
Abdominal part: Anterior layer of rectus sheath
|Insertions||Lateral lip of intertubercular sulcus of humerus|
|Innervation||Lateral and medial pectoral nerves (C5-T1)|
|Function||Shoulder joint: Arm adduction, Arm internal rotation, Arm flexion (clavicular head), arm extension (sternocostal head);|
Scapulothoracic joint: Draws scapula anteroinferiorly
|Clinical relations||Aplasia, Polan syndrome|