fill in the blank question\nthe abdominal and thoracic walls are drained by tributaries of two major veins…

Brief Explanations:

In human anatomy, the abdominal and thoracic walls are drained by tributaries of the internal thoracic vein and the inferior vena cava (in the abdominal region). However, more commonly for the walls, internal thoracic vein and azygos vein are considered major draining veins. The azygos vein drains the thoracic and abdominal walls on the right side and has tributaries that collect blood from these areas. The internal - thoracic vein drains the anterior thoracic wall and some of the abdominal wall structures.

Answer:

internal thoracic; azygos