**Core Concept:** Liver lobule is a functional unit of the liver consisting of a radial arrangement of hepatocytes (liver cells) surrounding the central vein. These hepatocytes are arranged in three zones: zone 1, zone 2, and zone 3, that differ in their blood supply and function.

**Why the Correct Answer is Right:** Zone 1 is more prone to ischemia because it receives a higher proportion of its blood supply from the hepatic artery, which carries oxygen-poor blood. In contrast, zones 2 and 3 are supplied primarily by the branches of the portal vein, carrying oxygen-rich blood. When there is a reduction in oxygen supply or increase in oxygen demand, zone 1 is more susceptible to ischemia.

**Why Each Wrong Option is Incorrect:**

A. Zone 2 is incorrect because it receives a significant amount of blood supply from both the hepatic artery and portal vein, making it less prone to ischemia compared to zone 1.

B. Zone 3 is incorrect because it also receives a significant amount of blood supply from the portal vein, making it less prone to ischemia compared to zone 1.

C. Zone 3 is not correct because it shares the same reasoning as option B, i.e., receiving a significant amount of blood supply from the portal vein, making it less prone to ischemia compared to zone 1.

**Clinical Pearl / High-Yield Fact:** Understanding the blood supply to the liver lobule is essential for understanding liver function, pathology, and clinical conditions such as liver cirrhosis, where the liver becomes resistant to portal blood flow, leading to increased risk of ischemia in zones 2 and 3 due to redistribution of blood flow.

**Correct Answer:** D. Zone 1 is more prone to ischemia due to its predominantly arterial blood supply.