Hi doctor , can please tell me if the chest mussels are inside the chest cavity or on top the ribs.

Outside: Your skeletal muscles of your chest are outside of the thorax ( chest cavity).

Mostly outside: The chest muscles that move the ribs are located on top of the ribs (outside the chest cavity) and in between the ribs. One can see this if he orders barbecued pork or beef ribs at a restaurant... The side with the meat is the outside, and the side with no meat is the inside. On the "no meat" side is the thin, shiny lining called the pleura.