Final answer:
The thoracic cavity contains the pleural cavities for the lungs and the mediastinal cavity, which includes the pericardial cavity for the heart, all protected by the ribcage and separated from the abdominopelvic cavity by the diaphragm.
Step-by-step explanation:
The thoracic cavity is a part of the human body enclosed by the ribcage, which contains vital organs such as the heart and lungs. Within the thoracic cavity, specific subdivisions play crucial roles in the respiratory and circulatory systems. The pleural cavities are two separate spaces that each envelop one lung, providing a protective cushion and space for the lungs to expand during inhalation. The mediastinal cavity is the central compartment of the thoracic cavity, housing the heart, thymus, esophagus, and trachea among other structures. Within the mediastinal cavity is the pericardial cavity, which contains the heart and provides it with a protective layer and space to beat without friction. The diaphragm, a muscular partition, forms the floor of the thoracic cavity and separates it from the abdominopelvic cavity. Together, these compartments and structures support the mechanics of breathing and protect the body's vital respiratory and circulatory organs.