Bilirubin: Hepatobiliary Anatomy and Physiology - Online (Rudinsky)

Question 1

Definition:
Is a useless and toxic breakdown product of hemoglobin

Answer 1

Bilirubin

Question 2

Bilirubin Beginnings:
Is conserved and efficiently recycled

Answer 2

Iron

Question 3

Bilirubin Beginnings:
Are protein and are catabolized and their components reused

Answer 3

Globin chains

Question 4

Bilirubin Beginnings:
What is the problem with hemoglobin?

Answer 4

Contains porphyrin called heme that cannot be recycled and must be eliminated

Question 5

Dead, damaged, and senescent red blood cells are picked up y phagocytic cells throughout the body (including Kuppfer cells in the liver) and digested
- Monocytic-macrophage system
- Heme processing/excretion

Answer 5

Bilirubin Beginnings

Question 6

Elimination of Heme:
Inside phagocytic cells, heme is converted through a series of steps into free bilirubin
- Free bilirubin is released into plasma where it is carried around bound to albumin (unconjugated bilirubin)

Answer 6

Step 1

Question 7

Elimination of Heme:
Free bilirubin is stripped off albumin and absorbed by hepatocytes
- Free bilirubin is conjugated to either glucuronic acid or sulfate (conjugated bilirubin)

Answer 7

Step 2

Question 8

Elimination of Heme:
Conjugated bilirubin is secreted into the bile canaliculus as part of bile and thus delivered to the small intestine
- Bacteria in the intestinal lumen metabolize bilirubin to a series of other compounds which are ultimately eliminated either in feces or, after reabsorption, in urine
- The major metabolite of bilirubin in feces is stercobilin which gives feces their characteristic brown color

Answer 8

Step 3

Question 9

What is the major metabolite of bilirubin in feces?

Answer 9

Stercobilin
- gives feces their characteristic brown color