Final answer:
Bilirubin is removed from the bloodstream by the liver, where it is processed and excreted in bile. When it reaches the intestine, it is converted into stercobilin and excreted in feces, giving stool its brown color.
Step-by-step explanation:
Bilirubin is created in the body as a byproduct of the recycling of red blood cells, primarily by the spleen. The non-iron portion of heme is degraded into biliverdin, a green pigment, and then into bilirubin, a yellow pigment. Bilirubin binds to albumin and is transported in the blood to the liver. In the liver, bilirubin is conjugated with glucuronic acid to form bilirubin diglucuronide, making it water soluble, and then excreted in the bile. It travels down the bile duct to the intestine, where intestinal bacteria transform it into stercobilinogen, and subsequently into stercobilin, a brown pigment that gives stool its characteristic color. This process is vital as high levels of bilirubin in the bloodstream can lead to jaundice, indicating liver malfunction.
The correct answer to the student's question on how bilirubin is removed from the bloodstream is b. the liver.