Here's a breakdown:
* Bilirubin: When red blood cells break down, they release hemoglobin. Hemoglobin is broken down into bilirubin, which is a yellow pigment.
* Liver Processing: The liver processes bilirubin and excretes it into the bile, which is released into the small intestine to help digest fats.
* Bacterial Action: In the intestines, bacteria convert bilirubin into urobilinogen.
* Stercobilin: Some urobilinogen is absorbed back into the bloodstream, but most of it is converted by bacteria into stercobilin, a brown pigment. Stercobilin is then excreted in the feces, giving it its characteristic brown color.
So, in summary, stercobilin, a byproduct of bilirubin breakdown by bacteria in the intestines, is the main pigment responsible for the brown color of feces.