Which of the following structures is located in the posterior mediastinum?

Explanation

## Mediastinal Divisions and Contents ### Mediastinal Compartments The mediastinum is divided into **superior** and **inferior** regions. The inferior mediastinum is further subdivided into **anterior**, **middle**, and **posterior** compartments. ### Posterior Mediastinum Contents **Key Point:** The posterior mediastinum lies behind the pericardium and contains: - **Esophagus** (main structure) - Descending thoracic aorta - Azygos venous system - Thoracic duct - Sympathetic chains and splanchnic nerves - Posterior mediastinal lymph nodes - Vagus nerves (descending portions) ### Comparative Mediastinal Contents | Compartment | Key Structures | |---|---| | **Superior** | Aortic arch, SVC, brachiocephalic vessels, trachea, esophagus (upper), thoracic duct | | **Anterior** | Thymus (in children), anterior mediastinal lymph nodes, connective tissue | | **Middle** | Heart, pericardium, main bronchi, pulmonary vessels, phrenic nerves | | **Posterior** | Esophagus, descending aorta, azygos system, thoracic duct, sympathetic chains | **High-Yield:** The esophagus is the **most characteristic structure** of the posterior mediastinum and is clinically important for esophageal procedures and pathology. **Clinical Pearl:** The posterior mediastinum is clinically significant because: - Esophageal pathology (cancer, strictures, achalasia) affects this region - Thoracic aortic aneurysms occur here - Posterior mediastinal masses are often neurogenic in origin (sympathetic chains) **Mnemonic:** **BEAT** (Posterior mediastinum) — Branches of aorta, Esophagus, Azygos system, Thoracic duct [cite:Gray's Anatomy 42e Ch Thorax]