Other than all of the things that I just mentioned the liver is important for, it’s also important for the production of something known as bile. This is a greenish liquid produced in the liver and stored in the gallbladder, which facilitates the digestion of fat. 

Bile, among other things, contains something known as bilirubin. Bilirubin is an orange-yellow pigment formed from the breakdown of red blood cells. Bilirubin is converted into other substances that eventually give urine its yellow color and feces its yellow-brown color. Who knew physiology could be so colorful and yet so disgusting? 

When red blood cells break down due to age or destruction, then something known as unconjugated or indirect or water-insoluble bilirubin is released into the bloodstream. Once this unconjugated bilirubin enters the liver, the liver converts it into conjugated or direct or water-soluble bilirubin by tacking on a compound known as glucuronic acid; this is what makes bilirubin water soluble. 

This newly water-soluble bilirubin is then secreted into the watery bile and, from there, into the intestines. 

If all of this is making your head spin, don’t worry; we can simplify it even more. Your liver is like a giant factory. Through one end, raw ingredients come in by the truckload. In our case, that’s crates and crates of raw, hard, and unprocessed indirect bilirubin. Once inside the factory, the workers take a piece of unconjugated bilirubin and stick another ingredient right onto it, thereby making an entirely new concoction, called conjugated bilirubin. This conjugated bilirubin isn’t hard like unconjugated bilirubin; it’s slushy and can dissolve easily in water instead.