What surrounds the thoracic cavity and contains vital organs such as the heart and lungs?

The thoracic cavity is encased by the thoracic cage, which consists of the ribs, thoracic vertebrae, sternum, and associated cartilages. This structure provides a protective enclosure for vital organs within the thoracic cavity, including the heart and lungs. The thoracic cage plays a crucial role in both protecting these organs and facilitating the mechanics of breathing by allowing the chest to expand and contract during inhalation and exhalation.

While the diaphragm is an essential muscle that separates the thoracic cavity from the abdominal cavity and aids in breathing, it does not surround the thoracic cavity itself. The rib cage is a component of the thoracic cage, as it refers specifically to the ribs that form part of the structure, but it does not encompass the whole assembly that includes the sternum and vertebral components. The sternum is a flat bone at the front of the thoracic cage, providing attachment points for ribs but not forming a complete enclosure by itself. Therefore, the thoracic cage is the most comprehensive and accurate term to describe the structure that surrounds and protects the thoracic cavity and its vital organs.