The mediastinum occupies the center of the thoracic cavity between the pulmonary viscera. It spans superiorly at the level of the thoracic aperture, inferiorly at the diaphragm, and from the sternum to the costal cartilages and bodies of vertebrae T1 to T12 antero-posteriosly.  With the exception of the lungs, the mediastinum involves all thoracic viscera.  For the purpose of description, the mediastinum is divided into superior, middle and inferior sections.  The heart, its roots of the great vessels (ascending aorta, pulmonary trunk, superior vena cava), and the pericardium occupy the middle mediastinum.
Anatomy of the heart
Cardiac cycle
Electrical conduction system of the heart
Hemodynamics
Coronary circulation
Renal function
Gastrointestinal physiology
Cerebral circulation