Pectoral muscles (colloquially referred to as "pecs") are the muscles that connect the front of the human chest with the bones of the upper arm and shoulder.
Pectoralis major is a thick, fan-shaped muscle, which makes up the bulk of the chest muscle. It lies under the breast. It serves to flex, extend, and rotate the humerus, the long bone of the upper arm.
Between the ribs are various groups of intercostal muscles, which help with breathing.
- Gray, Henry; Lewis, Warren (1918). Anatomy of the Human Body (twentieth ed.). Philadelphia and New York: Lea and Feibiger. Retrieved 13 September 2016.