Which structure separates the chest cavity from the abdominal cavity?

The diaphragm is a dome-shaped muscle that plays a crucial role in respiration and serves as the boundary between the thoracic (chest) cavity and the abdominal cavity. This muscular structure contracts and relaxes to facilitate breathing; during inhalation, it contracts and moves downward, increasing the volume of the chest cavity and allowing air to flow into the lungs. When it relaxes, it moves back up, helping to push air out of the lungs.

The diaphragm's positioning makes it effective at separating the two cavities, protecting the organs in the abdomen from pressure changes occurring within the thoracic cavity, and assisting in the mechanical aspects of breathing. It is the primary structure involved in creating the necessary pressure differentials for pulmonary ventilation.