Poal vein is formed by union of which of the following veins?
**Core Concept**
The portal vein is a vital structure in the hepatic portal system responsible for carrying blood from the gastrointestinal tract, gallbladder, and pancreas to the liver for detoxification and nutrient processing. The formation of the portal vein is crucial for maintaining liver function and overall digestion.
**Why the Correct Answer is Right**
The portal vein is formed by the union of the superior mesenteric vein and the splenic vein. This occurs behind the neck of the pancreas, where the two veins merge to form a single vessel. The superior mesenteric vein carries blood from the small intestine, while the splenic vein carries blood from the spleen and the stomach. The combined blood flow from these two veins is then directed to the liver for processing.
**Why Each Wrong Option is Incorrect**
* **Option A:** The hepatic portal vein is not formed by the union of the inferior mesenteric vein, which primarily carries blood from the rectum, sigmoid colon, and upper part of the rectum.
* **Option B:** The hepatic artery, not the hepatic portal vein, is primarily responsible for supplying oxygenated blood to the liver.
* **Option D:** The right gastric vein and the left gastric vein do drain into the portal vein, but they are not the primary contributors to its formation.
**Clinical Pearl / High-Yield Fact**
The portal vein is a critical structure in the hepatic portal system, and its obstruction can lead to severe complications, including portal hypertension and liver cirrhosis. Understanding the anatomy of the portal vein is essential for diagnosing and managing liver diseases.
**Correct Answer:** C.