Which muscle is responsible for breathing and separates the thoracic cavity from the abdominal cavity?

The diaphragm is primarily responsible for the process of breathing and serves as a crucial separator between the thoracic cavity, where the lungs are located, and the abdominal cavity, which contains the digestive organs.

During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity and allowing air to flow into the lungs. This action creates negative pressure in the thorax and enables efficient breathing. When the diaphragm relaxes during exhalation, it moves back to its dome shape, pushing air out of the lungs. The diaphragm's unique location and function make it essential for respiratory mechanics, distinguishing it from other muscles associated with movement or posture, such as the rectus abdominis, intercostal muscles, and pectoralis major, which serve different roles in the body.