Lying in it are heart, large vessels, esophagus, some nerves, and part of the network of branching tubes that carry air in and out of the lungs. Lungs have cardiac impression where heart sits between the lungs. In center of the mediastinal surface is area called the hilum or root of the lung. It admits vascular and respiratory structures. Convex surface of lung next to ribs called costal surface.
Right lung has also a transverse fissure.
On left lung the oblique fissure divides upper and lower lobes of lung. So, there are 5 lobes. Inner layer is pulmonary pleura. It adheres firmly to the lung. Pleural cavity is the potential, not actual space between the membrane.