Anatomy of the Thorax

Mediastinum

• Divided into Superior, Anterior, Middle, and Posterior parts
• Contains several structures, including the thymus gland, sternothyroid and sternohyoid muscles, and remnants of the thymus gland
• Boundaries: Anterior - body of sternum, Posterior - pericardium, Superior - imaginary line separating superior and inferior mediastinum, Inferior - diaphragm, Lateral - mediastinal pleura

Superior Mediastinum

• Contains the arch of aorta and its branches, brachiocephalic veins, and upper part of the superior vena cava (SVC)
• Also contains the trachea, esophagus, and thoracic duct
• Nerves present: right and left vagus, right and left phrenic, and left recurrent laryngeal nerve

Anterior Mediastinum

• Lies anterior to the pericardium
• Boundaries: Anterior - body of sternum, Posterior - pericardium, Superior - imaginary line separating superior and inferior mediastinum, Inferior - diaphragm, Lateral - mediastinal pleura
• Contains the sternopericardial ligament and mediastinal branches of the internal thoracic artery

Middle Mediastinum

• Contains the pericardium and heart
• Also contains the ascending aorta, pulmonary trunk, and bifurcation of the trachea into two main bronchi
• Nerves present: phrenic nerve and pericardiophrenic artery on the side of the pericardium
• Boundaries: Anterior - heart and pericardium, Posterior - thoracic vertebra, Inferior - diaphragm, Superior - imaginary line separating superior and inferior mediastinum

Posterior Mediastinum

• Contains the descending thoracic aorta, azygos vein, and thoracic duct
• Also contains the esophagus, sympathetic chain, and hemiazygos and accessory hemiazygos veins

Trachea

• Cartilaginous and fibromuscular tube, 10-12 cm long
• Begins from the lower border of the cricoid cartilage (C6) and ends at the level of the sternal angle (T4) by bifurcating into the right and left main bronchi
• During deep inspiration, the bifurcation extends to T6

Azygos Vein

• Begins at the back of the inferior vena cava (IVC) at the level of L2 or by the union of the right ascending lumbar vein and right subcostal vein opposite T12
• Tributaries include the common trunk formed by the right lumbar and right subcostal vein, right posterior intercostal veins, right superior intercostal vein, and others
• Clinical correlations: compression of the azygos vein can lead to mediastinitis, SVC syndrome, and compression of surrounding structures

This quiz covers the anatomy of the thorax, including veins, arteries, and other structures in the thoracic region.