**Question:** Choose the appropriate lettered structure in this CT scan of the abdomen at the level of the 12th thoracic vertebra. Which structure is divided into the proper hepatic and gastroduodenal arteries?

A. Aorta
B. Common hepatic artery
C. Arc of Riolan
D. Arcus aortae

**Core Concept:** In the abdomen, the aorta is a major vasculature structure that branches into several arteries, including the hepatic artery and duodenal artery. The hepatic artery supplies blood to the liver, while the gastroduodenal artery supplies blood to the stomach and duodenum.

**Why the Correct Answer is Right:** The correct answer, B (Common hepatic artery), is the branch of the abdominal aorta that divides into the proper hepatic artery and gastroduodenal artery. The proper hepatic artery supplies blood to the liver, while the gastroduodenal artery supplies blood to the stomach and duodenum. This division takes place at the level of the 12th thoracic vertebra, which is mentioned in the question.

**Why Each Wrong Option is Incorrect:**

A. Aorta (Arcus aortae) is the parent vessel that gives rise to the common hepatic artery, but it does not divide into the proper hepatic and gastroduodenal arteries.
C. Arc of Riolan is a collateral circulation found in the liver, not a specific artery.
D. Aorta (Arcus aortae) is the parent vessel that gives rise to the common hepatic artery, but it does not divide into the proper hepatic and gastroduodenal arteries.

**Clinical Pearl:** The understanding of arterial anatomy is crucial for interpreting CT scans, understanding surgical procedures, and managing complications related to these arteries, such as hepatic artery aneurysms.