Definition of Mediastinum. Mediastinum: The area between the lungs. The organs in the mediastinum include the heart and its large veins and arteries, the trachea, the esophagus, the bronchi, and lymph nodes. Search MedTerms:
The Pax Romana ended because the Roman state had ceased to grow. Boundaries had been set for the Empire, and for the first time the army had become a drain on the econom â¦ y of Rome. Till this point the army provided new slaves and riches from conqured countries.
The period known as the Pax Romana was a span of time that lasted  about 200 years in the Roman Empire. During this time, there was  peace and prosperity in this empire. It â¦ was established by  Augustus, and it began in 27 B.C. and ended about 180 A.D.