The pectoralis major (from Latin pectus 'breast') is a thick, fan-shaped or triangular convergent muscle of the human chest. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor muscle.
The pectoralis major is made up of 3 muscle bundles: the upper bundle (or clavicular), the middle bundle (or superior sterno-costal) and the lower bundle (or inferior sterno costal or abdominal)