|Origin||Clavicle, aponeurosis of the abdominal external oblique muscle, Sternum + upper 6 costal cartilages|
|Insertion||Lateral lip of Bicipital groove of Humerus|
|Nerve supply||Medical and Lateral Pectoral nerves|
|Actions||Flexion, Adduction and Medical rotation of arm|
Pectoralis major Origin and Insertions – Image modified from BodyParts3D, © The Database Center for Life Science licensed under CC Attribution-Share Alike 2.1 Japan
The Pectoralis Major muscle makes the bulk of chest muscles. It originates from 3 different zones – Clavicular, Abdominal and Sterno-costal. Check the images above.
Regarding actions, if the muscle contracts what happens to the Humerus? As it’s attaching on the front side of bone, you’ll expect some rotation to happen.