In this article, we shall look at the anatomy of the posterior mediastinum – its borders, contents and clinical correlations. Borders The posterior mediastinum is bordered by the following thoracic structures: 1  Lateral: Mediastinal pleura (part of the parietal pleural membrane). 2  Anterior: Pericardium. 3  Posterior: T5-T12 vertebrae. 4  Roof: Imaginary line extending between the sternal angle (the angle formed by the junction of the sternal body and manubrium) and the T4 vertebrae.