bilirubin

(bĭl-ĭ-roo′bĭn)

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[bili- + L. ruber, red + -in]
C33H36O6N4; the yellow, brown or orange pigment in bile. It is derived metabolically from hemoglobin. A small amount is always present in plasma because of the breakdown of red blood cells. It is carried to the liver by the blood. There it is conjugated (made soluble in water) and excreted in the bile via the duodenum. As it passes through the intestines, some of it is converted into urobilinogen by bacterial enzymes, but most of it is excreted in feces. If urobilinogen passes into the circulation, it is excreted through the urine or reexcreted in the bile. The pathological accumulation of bilirubin in the body produces jaundice.

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