boundary and divisions Thoracic cage: consist of sternum, ribs, thoracic vertebrae and their articulations The thoracic wall: consist of the thoracic cage, skin, fasciae, muscles, blood vessels and nerves The thoracic cavity: it is divided into two parts by the mediastinum. The cavities on each side are occupied by the lungs and pleural sac Mediastinum: is generally defined as the intervals between the right and left pleural sacs. jugular notch sternoclavicular manubrium stemi jugular notch sternal angle Brd costal cartilage body of stern 9th rb -7th sternocostal j angle of Louis costal margin Thoracic cage: consist of sternum, ribs, thoracic vertebrae and their articulations.  The thoracic wall: consist of the thoracic cage, skin, fasciae, muscles, blood vessels and nerves.  The thoracic cavity: it is divided into two parts by the mediastinum. The cavities on each side are occupied by the lungs and pleural sac.  Mediastinum：is generally defined as the intervals between the right and left pleural sacs. boundary and divisions