Anatomical divisions of the mediastinum

Mediastinum is located between the two pleural cavities and lungs. A line from the sternal angle to the lower border of fourth thoracic vertebra divides it into superior and inferior mediastinum. Heart is located in the inferior mediastinum. Inferior mediastinum is further divided into anterior, middle and posterior mediastinum. Superior mediastinum contains great vessels, trachea and upper part of the oesophagus. Thymus, thoracic duct, phrenic and vagus nerves are also present in the superior mediastinum. Anterior mediastinum between the heart and the sternum may contain part of the thymus in children, a few lymph nodes and connective tissue. Middle mediastinum contains the heart enclosed in the pericardial cavity, ascending aorta, parts of superior and inferior vena cava, pulmonary arteries and veins, tracheal bifurcation and main bronchi. Posterior mediastinum contains the descending thoracic aorta, parts of oesophagus, thoracic duct, azygos and hemiazygos veins, vagus nerves and sympathetic trunks. Parts of these structures are also present in the superior mediastinum.