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Laboratory 21. Mediastinum
Step 1. The Anterior Mediastinum

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The anterior mediastinum is bounded anteriorly by the posterior surface of the sternum and costal cartilages, and posteriorly by the anterior border of the pericardium. Identify the principal structures of the anterior mediastinum.
  • Remnants of the thymus gland are embedded in fat and extend from the superior mediastinum into the anterior mediastinum. In early childhood, the thymus gland is active and reaches its largest in size. In the aged adult it is often small and embedded in fat.
  • The internal thoracic vessels lie adjacent to the sternum.
  • The parasternal lymph nodes, (or internal thoracic nodes) [cross-section] are associated with the internal thoracic vessels in the intercostal spaces adjacent to the sternum.