• A membrane in the midline of the THORAX of mammals. It separates the lungs between the STERNUM in front and the VERTEBRAL COLUMN behind. It also surrounds the HEART, TRACHEA, ESOPHAGUS, THYMUS, and LYMPH NODES.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2025
• An anatomic site along the midline and under the sternum that contains the heart and pericardium, the bases of the great vessels, the trachea and bronchi, esophagus, thymus, lymph nodes, thoracic duct, phrenic and vagus nerves, and other structures and tissues.
  NCI
  U.S. National Cancer Institute, 2021
• Mass of tissues and organs separating the two pleural sacs, between the sternum anteriorly and the vertebral column posteriorly and from the thoracic inlet superiorly to the diaphragm inferiorly; contains the heart, pericardium, the bases of the great vessels, the trachea and bronchi, esophagus, thymus, lymph nodes, thoracic duct, and the phrenic and vagus nerves.
  CRISP Thesaurus
  National Institutes of Health, 2006
• Subdivsion of thoracic compartment which has as its parts the superior mediastinum and inferior mediastinum.
  Foundational Model of Anatomy
  University of Washington, 2017
• The area between the lungs. The organs in this area include the heart and its large blood vessels, the trachea, the esophagus, the thymus, and lymph nodes but not the lungs.
  NCI Dictionary of Cancer Terms
  U.S. National Cancer Institute, 2021
• The central region of the thoracic cavity of mammals containing a group of organs surrounded by loose connective tissue, which separates the two pleural sacs.
  CDISC Terminology
  Clinical Data Interchange Standards Consortium (CDISC), 2021
• Mediastinum, the anatomic region located between the lungs that contains all the principal tissues and organs of the chest except the lungs. It extends from the sternum, or breastbone, back to the vertebral column and is bounded laterally by the pericardium, the membrane enclosing the heart, and...
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2025