Gross Anatomy: Thorax 3

Gross Anatomy: Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura

• Posterior Mediastinum Boundaries: Superior - transverse thoracic plane (sternal angle and junction of T4 and T5 vertebrae); Inferior - diaphragm; Anterior - pericardium; Posterior - T5-T12 vertebrae; Lateral - Mediastinal Pleurae.
• Posterior Mediastinum Contents: Thoracic Aorta (blood supply, venous drainage, nerve, lymphatic drainage), Esophagus (blood supply, venous drainage, nerve supply, lymphatic drainage), thoracic duct, azygos vein, hemi-azygos vein, thoracic sympathetic trunk.
• Trachea: Tubular structure about 25 cm (10 in.) long, beginning at the lower border of the cricoid cartilage, descending in the midline, ending at the sternal angle, dividing into right and left principal bronchi (blood supply, venous drainage, nerve supply, lymphatic drainage).
• Bronchi: Right principal bronchus wider, shorter, and more vertical than the left (blood supply, venous drainage, nerve supply, lymphatic drainage); Left principal bronchus narrower, longer, and more horizontal (blood supply, venous drainage, nerve supply, lymphatic drainage)
• Lungs: Right lung slightly larger, divided into superior, middle, and inferior lobes; Left lung divided into superior and inferior lobes; Surfaces - Costal, diaphragmatic, mediastinal; Root of lung, structures entering/leaving lung.
• Pleura: Two layered membrane (visceral and parietal), costal, diaphragmatic, mediastinal pleura; pleural recesses (costal and costomediastinal); blood supply, venous drainage, nerve supply, lymphatic drainage; Suprapleural membrane (Sibson's fascia) lines undersurface of the suprapleural membrane.
• Thoracic Aorta Branches: Esophageal, bronchial, pericardial, mediastinal, superior phrenic, subphrenic, posterior intercostal arteries.
• Esophagus: Tubular structure about 25 cm (10 in.) long; beginning at the level of C6; Three segments (Cervical, Thoracic, Abdominal); Physiologic constrictions (at the junction of the pharynx and esophagus C6, T4, T10). Structures accompanying it in the diaphragm opening: vagus nerves, branches, and also, tributaries of the left gastric blood vessels, and lymphatic vessels.
• Thoracic Duct: Begins in the abdomen as the cisterna chyli, ascends through the aortic opening, runs upward along the left edge of the esophagus to enter the junction of the left internal jugular vein and left subclavian vein, collecting lymph from lower limbs, pelvis, abdomen etc.
• Azygos Vein: Arises from the posterior aspect of the inferior vena cava, forms collateral pathway between superior and inferior vena cava, draining blood from the posterior walls of the thorax and abdomen, ascending in the posterior mediastinum, arching over the root of right lung to join the superior vena cava.
• Hemiazygos Vein: Arising on the left side from the junction of the left subcostal and ascending lumbar veins. Ascends on the left side of the vertebral column, crosses to the right and joins the azygos vein.
• Nerve Supply of Lungs: Pulmonary plexus.
• Lymphatic Drainage of Lungs: Bronchopulmonary nodes, tracheobronchial nodes, bronchomediastinal trunks. Superficial and deep plexus.
• Blood Supply of Lungs: Bronchial arteries (branch of descending thoracic aorta).
• Venous Drainage of Lungs: Pulmonary veins, drained into the left atrium, bronchial veins (communicate with pulmonary veins) and enter the azygos and hemiazygos veins.
• Nerve Supply of Esophagus: parasympathetic and sympathetic fibers via vagus nerves and sympathetic trunk.
• Lymphatic Drainage of Esophagus: Upper third into deep cervical nodes; middle third into superior/posterior mediastinal nodes; lower third into nodes along left gastric blood vessels and celiac nodes.
• Blood Supply of Esophagus: Upper third - inferior thyroid artery; Middle third - descending thoracic aorta; Lower third - left gastric artery.
• Venous Drainage of Esophagus: Upper third - inferior thyroid veins; Middle third - azygos vein; Lower third - left gastric veins (tributary of portal vein).

Explore the complexities of the thorax with our quiz on the posterior mediastinum, trachea, bronchi, lungs, and pleura. Delve into boundaries, contents, and anatomical structures, enhancing your understanding of thoracic anatomy.