What does the term 'internal' specifically indicate?

The term 'internal' specifically indicates something that is located within the body. In anatomical and physiological contexts, this term is used to describe structures, organs, or processes that occur inside the body, as opposed to those that are external or on the surface. For instance, the internal organs include the heart, lungs, and intestines, all of which are essential components functioning within the body’s systems. This distinction is crucial for understanding human anatomy and the location of various systems and their interactions.