**Posterior Mediastinum: Oesophagus & Descending Thoracic Aorta **
1. Describe the morphology and relations of the oesophagus
- The oesophagus is a muscular tube that extends from the pharynx to the stomach.
- It is approximately 25 cm long and has three distinct parts: cervical, thoracic, and abdominal.
- The cervical part is about 15 cm long and lies in front of the vertebral column, with the trachea and thyroid gland lying anterior to it.
- The thoracic part is about 20 cm long and lies in the posterior mediastinum, with the trachea and bronchi anterior to it.
- The abdominal part is about 15 cm long and lies in the posterior mediastinum, with the diaphragm and stomach anterior to it.
2. Mention constrictions in its course
- There are three constrictions in the course of the oesophagus:
- Upper constriction: where the oesophagus passes through the cricoid cartilage (C6).
- Middle constriction: where the oesophagus passes behind the aortic arch (T4-T5).
- Lower constriction: where the oesophagus passes through the diaphragm (T10).
3. Mention the blood supply and nerve supply
- Blood supply: the oesophagus is supplied by the oesophageal branches of the aorta and the inferior thyroid arteries.
- Nerve supply: the oesophagus is supplied by the vagus nerves (both sympathetic and parasympathetic).
4. Describe the extent, branches, and relations of the descending thoracic aorta
- The descending thoracic aorta extends from the aortic arch to the diaphragm (T4-T12).
- It gives off four pairs of intercostal arteries and three pairs of posterior intercostal arteries.
- The descending thoracic aorta lies in the posterior mediastinum, posterior to the oesophagus and trachea.
5. Describe the applied anatomy
- The oesophagus and descending thoracic aorta are both important structures in the posterior mediastinum.
- Knowledge of their morphology and relations is essential for surgical procedures such as oesophagectomy and thoracic aortic aneurysm repair.
- Understanding the blood supply and nerve supply of the oesophagus is also crucial for managing oesophageal disorders.