**Core Concept**
The vitelline veins are a group of veins that develop in the embryo, playing a crucial role in the formation of the portal venous system. They are responsible for draining the yolk sac and eventually contribute to the formation of the hepatic portal vein.

**Why the Correct Answer is Right**
During embryonic development, the vitelline veins form a network of vessels that connect the yolk sac to the heart. As the embryo grows, these veins undergo significant changes, eventually fusing to form the hepatic portal vein, which carries blood from the gastrointestinal tract to the liver. This process is essential for the development of the portal venous system, which is crucial for nutrient exchange and detoxification.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the vitelline veins do not form the umbilical veins. The umbilical veins, on the other hand, are responsible for carrying oxygenated blood from the placenta to the embryo.
* **Option B:** This option is incorrect because the vitelline veins do not form the hepatic veins. The hepatic veins are responsible for draining deoxygenated blood from the liver to the inferior vena cava.
* **Option C:** This option is incorrect because the vitelline veins do not form the superior mesenteric vein. The superior mesenteric vein is a tributary of the hepatic portal vein, but it is not formed by the vitelline veins.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the vitelline veins play a critical role in the development of the portal venous system, which is prone to portal hypertension and varices in adults.

**Correct Answer: A. The vitelline veins form the hepatic portal vein.**