What best describes the heart based on its location and functions?

The heart is best described as internal because it is located within the thoracic cavity, protected by the rib cage and surrounded by other vital organs. Its placement allows it to efficiently pump blood throughout the body while being shielded from external injury. The term "internal" indicates that it is not visible from the outside and plays a critical role in maintaining circulation and supplying oxygen to tissues. This definition emphasizes the heart's essential functions related to internal body processes, distinguishing it from terms that suggest visibility or proximity to the surface of the body.