The __________ is a domed-shaped muscle that separates the thoracic and abdominal cavities.

The diaphragm is a crucial muscle in the human body, functioning primarily in the respiratory process. It is a domed-shaped muscle located below the lungs and above the abdominal cavity, serving as the primary separator between these two regions. When you inhale, the diaphragm contracts and flattens, creating a vacuum that allows air to flow into the lungs. Conversely, when exhaling, the diaphragm relaxes and returns to its dome shape, which helps push air out of the lungs.

This anatomical positioning and function not only emphasize the diaphragm's role in respiration but also highlight its significance as a barrier between the thoracic and abdominal cavities. Each of the other muscles mentioned, such as the intercostal muscles, rectus abdominis, and transverse abdominis, serves distinct purposes related to movement and posture but does not share the same critical role in separating the thoracic and abdominal cavities as the diaphragm does.