Bilirubin is an orange pigment formed by the liver as a result of heme breakdown and excreted in the bile.

• A. A blue pigment produced by the spleen
• B. An orange pigment formed by the liver as a result of heme breakdown and excreted in the bile
• C. A yellow pigment produced by the kidneys
• D. A green pigment produced by bile

Answer: (B)

Bilirubin is the orange-yellow pigment that comes from the breakdown of heme in aged red blood cells. After heme is released, it is converted first to biliverdin and then to bilirubin. This bilirubin is carried to the liver, where it is conjugated to become water-soluble and then excreted into the bile. This excretion into bile explains why bilirubin is associated with bile and stool coloration, and why excess bilirubin can lead to jaundice when it accumulates in the blood.

So describing bilirubin as an orange pigment formed from heme breakdown in the liver and excreted in bile matches its true origin and fate. Other options describe pigments that aren’t the primary bile pigment: a blue pigment from the spleen isn’t a standard description of bilirubin physiology, a yellow pigment produced by the kidneys misattributes the origin to the kidneys, and a green pigment produced by bile aligns more with biliverdin, an intermediate in heme breakdown, not the pigment ultimately excreted into bile as bilirubin.