Q. A 56-year-old man is diagnosed with renal cell carcinoma of the right kidney. The patient's past medical history is significant for hypertension. He smoked 30 cigarettes/day for the last 20 years. The tumor is believed to be non-resectable due to the invasion of a venous structure passing through the diaphragm. Which of the following embryological derivatives is considered the origin of this venous structure?