Thoracic cavity

The thoracic cavity or the chest cavity lies between the neck and the abdomen. It is bounded by the thoracic wall and extends from the diaphragm (below) to the superior thoracic aperture (above). The latter comprises of the first thoracic vertebrae, upper border of manubrium sterni and the first ribs on either side. Anteriorly, the thoracic cavity is limited by the sternum, while posteriorly it is bounded by the thoracic part of the vertebral column.

The thoracic cavity is divided into two compartments. These include the mediastinum in the center, bounded by a pleural cavity on either side. The pleural cavities house the lungs inside them. Whereas, the mediastinum contains heart and the associated big vessels, and several important structures enlisted below.

The mediastinum can be sub-divided into superior and inferior mediastinum with the help of an imaginary thoracic plane passing through sternal angle in the front and the lower border of fourth thoracic vertebrae behind. The inferior mediastinum can be further sub-divided into anterior, middle and posterior mediastinal regions. The middle mediastinum lies within the confines of the pericardial sac, containing heart and its big vessels, while the anterior and posterior mediastinum lie in front of and behind the pericardial sac, respectively.

The important structures contained within various compartments of the thoracic cavity encompass:

• Lungs and pleura → inside pleural cavities,

• Heart, roots of great vessels, phrenic nerve and pericardium → inside middle mediastinum,

• Thymus and lymph nodes → inside anterior mediastinum,

• Descending aorta, azygous and hemiazygos veins, esophagus, vagus nerves, sympathetic trunk, thoracic lymphatic duct → inside posterior mediastinum,

• Trachea and all structures inside the posterior mediastinum extend into it from the superior mediastinum