- At level of 2nd Costal Cartilages
- Level of lower border of T4
- Above this level up to the Thoracic Inlet = Superior Mediastinum
- Below this level = Inferior Mediastinum – divided into 3 parts by the Fibrous Pericardium – Anterior, Middle and Posterior
- Landmarks at this level:
- Bifurcation of the Trachea
- Concavity of the Arch of the Aorta
- Just above the bifurcation of the Pulmonary Trunk
- Azygos Vein enters the Superior Vena Cava
- Thoracic Duct reaches the Left Side of the Oesophagus
- Ligamentum Arteriosum with the Left Recurrent Laryngeal Nerve recurving below it
- Tracheobronchial Lymph Nodes
- Superficial and Deep Parts of the Cardiac Plexus
