Anatomy, Thorax, Lung Pleura And Mediastinum

A pleura is a serous membrane that folds back on itself to form a two-layered membranous pleural sac. The outer layer is called the parietal pleura and attaches to the chest wall. The inner layer is called the visceral pleura and covers the lungs, blood vessels, nerves, and bronchi. There is no anatomical connection between the right and left pleural cavities. See Lung Anatomy. With the addition of pleural fluid, the lung pleura allows for easy movement of the lungs and inflation during breathing.  The mediastinum is a central compartment in the thoracic cavity between the pleural sacs of the lungs (see  The Mediastinum, Transverse Section of the Thorax). It is divided into two major parts, the superior and inferior portions. The inferior portion is then further divided into the anterior, middle, and posterior portions. Each region of the mediastinum contains specific groups of structures. See Mediastinal Divisions. : Superior mediastinum: Organs: thymus, trachea, esophagus; Arteries: aortic arch, brachiocephalic trunk, left common carotid artery, left subclavian artery; Veins and lymphatics: superior vena cava, brachiocephalic vein, thoracic duct; Nerves: vagus nerve, left recurrent laryngeal nerve, cardiac nerve, phrenic nerve. Anterior mediastinum: Organs: thymus; Arteries: small arterial branches; Veins and lymphatics: small branches; Nerves: none. Middle mediastinum: Organs: heart, pericardium; Arteries: ascending aorta, pulmonary trunk, pericardiacophrenic arteries; Veins and lymphatics: superior vena cava, azygos vein, pulmonary vein, pericardiacophrenic vein; Nerve: phrenic. Posterior mediastinum: Organs: esophagus; Arteries: thoracic aorta; Veins and lymphatics: Azygos vein, hemiazygos vein, thoracic duct; Nerve: the vagus nerve. .