SadandFurious

SadandFurious t1_irbpm78 wrote

To add on to others, the reason your skin tends to look yellow as bruises progress is because of biliverdin (green pigment)/bilirubin (yellow), 2 intermediate products in the breakdown process of the heme group, which is the iron-containing, red pigment, O2 carrying part of hemoglobin in red blood cells (RBCs).

This is in essence the same reason people with liver failure and hemolytic disease (diseases that destroy RBCs) tend to have yellowing of their skin and eyes (jaundice). Macrophage (big eater) cells in the spleen/liver eat and break down old RBCs, and the resulting bilirubin is conjugated into a soluble form and excreted in bile, which helps emulsify fats in your small intestine.

We can take this even further- the bilirubin is eventually converted by gut bacteria into stercobilin, which makes poop brown, and urobilinogen, which is partly reabsorbed and leaves through the kidneys as urobilin, which makes pee yellow. So as you can see, that heme group in hemoglobin responsible for coloring a lot of our fluids.

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