The thoracic structures refer to the components located within the thoracic cavity, which is the area of the body between the neck and the abdomen. This cavity houses vital organs, including the heart and lungs, and is protected by the rib cage. The thoracic cavity is divided into three main parts: the left and right pleural cavities, which contain the lungs, and the mediastinum, which contains the heart, trachea, and esophagus. The thoracic structures also include various muscles, such as the intercostal muscles, which assist in breathing by expanding and contracting the rib cage. Additionally, the diaphragm plays a crucial role in respiration, separating the thoracic cavity from the abdominal cavity. These structures work together to facilitate essential functions like breathing and circulation.