Mediastinum Anatomy PDF

Mediastinum Introduction Lateral view of Thorax  Mediastinum A median septum or median partition between the two pleural cavities.  Boundaries of the Mediastinum Superior boundary: Superior thoracic aperture Inferior boundary: Diaphragm Anterior boundary: Sternum Posterior bou...

Mediastinum Introduction Lateral view of Thorax  Mediastinum A median septum or median partition between the two pleural cavities.  Boundaries of the Mediastinum Superior boundary: Superior thoracic aperture Inferior boundary: Diaphragm Anterior boundary: Sternum Posterior boundary: Bodies of vertebrae T1 to T12 Lateral boundaries: Mediastinal parietal pleura (left and right).  Divisions of Mediastinum 1. Superior mediastinum: Above the imaginary plane between the manubrium sterni and the lower border of the 4th thoracic vertebra.  Divisions of Mediastinum 2. Inferior mediastinum: Below the imaginary plane and it is further subdivided into: a. Anterior mediastinum: Behind the body and xiphoid process of the sternum and in front of the middle mediastinum (pericardium). b. Middle mediastinum: Contains pericardium, heart and the roots of the great vessels. c. Posterior mediastinum: Lies behind the middle mediastinum (the part that lies posterior to the pericardium and anterior to the bodies of vertebrae T5 to T12). Mediastinum  Boundaries A) Ant– sternum B) Post—vertebral column C) Sup—Thoracic inlet D) Inf—Diaphragm E) On each side— Mediastinal pleura.  Types A) Superior mediastinum B) Inferior mediastinum 1) Anterior 2) Middle 3) Posterior  Superior mediastinum 1) Boundaries Ant– Manubrium sterni Post—Upper 4 thoracic vertebrae Sup– Plane of thoracic inlet Inf—An imaginary plane passing through the sternal angle in front, & the lower border of the body of the 4th thoracic vertebra. On each side– Mediastinal pleura  Contents 1) Trachea & oesophagus 2) Muscles origins of sternohyoid, sternothyroid, lower ends of longus colli. 3) Arteries Arch of aorta, Brachiocephalic , left common carotid, left subclavian. 4) Veins upper half of the svc, left superior intercostal vein 5) Nerves—vagus, phrenic, cardiac, left recurrent laryngeal 6) Thymus 7) Thoracic duct 8) lymphnode– paratracheal, Brachiocephalic, Tracheobronchial  Anterior Mediastinum Boundaries Ant— body of sternum Post— pericardium Sup— imaginary plane separating the sup mediastinum from the inferior mediastinum Inf– superior surface of diaphragm On each side– mediastinal pleura  Contents A) Sternopericardial ligament B) Internal thoracic artery (Small mediastinal branches) C) Thymus (Lowest part) D) Areolar tissue E) Lymph nodes & lymphatics  Sternopericardial ligament  Middle Mediastinum Boundaries Ant– pericardium Post—oesophagus, descending thoracic aorta, azygos vein On each side– Mediastinal pleura Contents 1) Heart 2) Veins –svc, azygous,pulmo 3) Nerves-phrenic,deep cardiac 4) Tracheobronchial lymph nodes.  Azygos vein The azygos vein is a vein running up the side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blood to the right atrium when either of the venae cavae is blocked.  Azygos vein The azygos vein transports deoxygenated blood from the posterior walls of the thorax and abdomen into the superior vena cava vein. The anatomy of this blood vessel can be quite variable. In some rare variations for example, it also drains thoracic veins, bronchial veins and even gonadal veins. The vein is so named because it has no symmetrically equivalent vein on the left side of the body.  Azygos vein It is formed by the union of the ascending lumbar veins with the right subcostal veins at the level of the 12th thoracic vertebra, ascending in the posterior mediastinum, and arching over the right main bronchus posteriorly at the root of the right lung to join the superior vena cava. This "arch of the azygos vein" (arcus venae azygos) is an important anatomic landmark. Azygos vein As an anatomical variation in 1-2% of the population, the arch can be displaced laterally, thereby creating a pleural septum separating an azygos lobe from the upper lobe of the right lung. arch of the azygos vein  Posterior Mediastinum Boundaries Ant—pericardium, trachea, pulmonary vessels, diaphragm. Post—8 th thoracic vertebrae & intervening discs. On each side—Mediastinal pleura  Contents 1) Oesophagus 2) Arteries—descending thoracic aorta & its branches 3) Veins—azygous , hemiazygous, accessory hemiazygous vein 4) Nerves—vagus, splanchnic, greater, lesser & least splanchinc nerves arising from the lower 8th thoracic ganglia of the sympathetic chain 5) Lymph nodes– post mediastinal lying alongside the aorta & thoracic duct  Clinical Anatomy 1) Mediastinitis 2) Mediastinal syndrome Symptoms 1. Engorgement of veins in the upper half of the body 2. Dyspnea, cough 3. Dysphagia 4. Hoarseness of voice 5. Intercostal neuralgia 6. Erosion of the vertebral bodies 7. Paralysis of the diaphragm  Mediastinal syndrome Mediastinal syndromes are a group of disorders characterized by infiltration, entrapment or compression of mediastinal structures. Superior vena cava syndrome is the most severe complication of mediastinal syndromes and is considered to be a medical emergency.