Final answer:
Superior Vena Cava Syndrome is a condition where the superior vena cava is compressed by a mediastinal mass, impeding blood flow from the upper body to the heart.
Step-by-step explanation:
The Superior Vena Cava Syndrome (SVCS) is a medical condition that occurs when the superior vena cava, a large systemic vein that returns blood to the heart from the superior portion of the body, is compressed by a mediastinal mass such as lung cancer or lymphoma. This vein is crucial in the systemic circuit as it handles the blood flow from the upper parts of the body, including the arms and head, back to the right atrium of the heart. If SVCS occurs, blood flow can be significantly obstructed, leading to swelling and a plethora of other symptoms in the upper extremities and face due to blood accumulation and increased venous pressure. Conditions like hypertrophy, hyperplasia, hypoxia, and hypervolemia are often associated with the systemic circulation's adaptation or reaction to such obstructions.