Q43 — Liver Lobule Zonation and Bile Flow

Theoretical B Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license

In the liver lobule, 75% of the blood comes via the portal vein located within the portal triad, and 25% comes from the hepatic artery. The portal triad consists of a hepatic artery, a portal vein, and a bile duct. The portal vein carries blood from the intestine and stomach, while the central veins carry blood away from the liver cells. Functionally, in the lobule there are zones: 1, 2, 3 (Figure 1A). Figure 1C shows bile flow in different animals.

Figure 1. A S — portal triad; Q — central vein; 1 — periportal zone; 2 — middle zone; 3 — perivenous zone. B Y — circulating toxic substance concentration (%); X — distance from the central vein. C Y — bile flow (µL/kg/min); X — bile salt secretion (µmol/kg/min); A — rabbit, B — rat, C — human (“kg” in units refers to kg of liver).

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. In a person suffering from prolonged hypoxia, zone 2 will mainly be affected due lack of oxygen.

B. If a person accidentally intakes an organic toxic substance, then Line P will display its relative concentrations in the liver lobule.

C. If both rabbits and rats are in a situation unable to secrete any bile salts, then bile flow will be lower in rabbits.

D. A student (with liver mass = 1.5 kg, bile production rate = 17 µL/g Liver/h) will produce 17 ml of bile after 40 min of solving IBO questions.

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Question reproduced from IBO 2024, Theoretical Exam Part B, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF