Mediastinum Anatomy

Introduction

• Presenter: Dr. Morton, noted anatomist
• Topic: Mediastinum and its regional anatomy

Definition

• Mediastinum: Midway area between the lungs, usually includes the region situated between the sternum (front) and vertebrae (back), and extends from the first rib down to the diaphragm.

Regions of the Mediastinum

1. Superior Mediastinum: Area between the first rib and the transverse thoracic plane
2. Inferior Mediastinum: Extends from the transverse thoracic plane to the diaphragm, further divided into:
   • Anterior Mediastinum: Contains the thymus.
   • Middle Mediastinum: Contains the pericardial sac and heart.
   • Posterior Mediastinum: Located behind the heart, including major vessels and nerves.

Focus of the Lecture

• Concentration on the superior and posterior mediastinum, excluding the anterior and middle regions previously covered.

Posterior Mediastinum Anatomy

• Likened to the area behind a living room TV, filled with "wires" or structures organized behind the heart.
• Structures (acronym DATES):
  • Descending aorta
  • Azygos system of veins
  • Thoracic duct
  • Esophagus
  • Sympathetic nerves

Descending Aorta

• Extends from the aortic arch down through the thoracic cavity, supplying posterior intercostal arteries to every segmental level.

Azygos System of Veins

• Includes the azygos vein, accessory hemiazygos vein, and hemiazygos vein, draining blood from thoracic and abdominal back walls.

Thoracic Duct

• Largest lymphatic vessel in the body, transports about 4 liters of lymph per day.

Esophagus

• Conducts food from the throat to the stomach, accompanied by the vagus nerve.

Sympathetic Nerves

• Includes the sympathetic chain and ganglia, and splanchnic nerves affecting various body organs.

Superior Mediastinum Anatomy

• Divided into three planes: venous, arterial, and visceral.

Venous Plane

• Formed by the internal jugular and subclavian veins merging into the brachiocephalic veins, which then form the superior vena cava.

Arterial Plane

• Includes the aortic arch and its primary branches supplying the arms, head, and brain.

Visceral Plane

• Contains the trachea (windpipe) and esophagus (food pipe).

Conclusion

• The mediastinum, particularly the superior and posterior segments, is critical for understanding the thoracic region's vascular and nervous anatomy.