Four division of the mediastinum

Answer 1

the newest nomenclature says that mediastinum is divided in 4 parts: -mediastinum anterius, -mediastinum posterius, -mediastinum superius and -mediastinum inferius. Mediastinum inferius is divided in 3 parts (anterius, medius and posterius);

Answer 2

The esophagus, trachea, main stem bronchi, The heart and great vessels.

IF I recall correctly, the great vessels are the aorta, vena cava, right & left pulmonary arteries.