heme recycling

a

heme breaks down into bilirubin (green color) in macrophage (often in the spleen)

b

biliverdin broken down into bilirubin (yellow color) in macrophage. bilirubin is a waste product, where it builds up, we get a yellow cast on own skin, nail beds and sclera

c

bilirubin gets transferred to the liver via the bloodstream

d

liver excretes bilirubin into small intestine via bile

e

bacterial activity in the large intestine which breaks bilirubin down into urobilinogen

f

urobilinogen travels to the kidneys in the blood stream, becomes urobilin and its excreted in urine, that’s why we pee yellow

g

leftover urobilinogen in the large intestine is broken down into stercobilin (brown color), why feces is brown