What is the name of the structure that separates the thoracic cavity from the abdominal cavity?

The diaphragm is a dome-shaped muscular structure that plays a crucial role in respiration and is the barrier that separates the thoracic cavity from the abdominal cavity. During inhalation, the diaphragm contracts and flattens, allowing the chest cavity to expand and draw air into the lungs. In this anatomical context, it functions as a partition, creating distinct thoracic and abdominal spaces.

The intercostal muscles, although important for the mechanics of breathing, primarily assist with the expansion of the rib cage and do not serve as a separation between the two cavities. The sternum, a flat bone located in the center of the chest, provides a point of attachment for ribs but does not separate the cavities. The pericardium is a fibrous layer that encases the heart, also unrelated to the division between the thoracic and abdominal cavities. Thus, the diaphragm is accurately identified as the correct structure dividing these two regions.