The diaphragm is made up of muscle tissue. What factor leads to this conclusion?

The diaphragm, separating the abdominal and chest cavities, is a necessary part of the respiratory process. Outwardly, breathing is defined as the movement of the thoracic and abdominal regions. These movements are due to the work of the diaphragm. As you inhale, it contracts, which allows the lungs to expand. As you exhale, the diaphragm relaxes and compresses the lungs. This fact suggests that the diaphragm is a muscle, since the main feature of any muscle tissue is its ability to contract. In the body, this muscle is the most powerful.