The common name for the muscle that protects the heart is the diaphragm. However, it is essential to clarify that while the diaphragm's primary role is in respiration, it does not "protect" the heart in a conventional sense. The diaphragm is a dome-shaped muscle located beneath the lungs. When it contracts, it allows the lungs to expand, aiding in the intake of air. The actual protective structures of the heart include the ribcage, which shields it from physical trauma. The heart itself is also encased in a protective layer known as the pericardium, ensuring its safety and proper function within the chest cavity.