Fate of Old Erythrocytes

Question 1

Lifespan of erythrocytes

Answer 1

RBCs last a lot longer than other blood cells
- Ex. ruminants and horses ~140days (horses 145)
- Ex. Dogs 118 days
- Ex. Cats 75 days
- Ex. chicken 30 days

Question 2

Why do erythrocytes die?

Answer 2

• They have no nucleus or RNA, so cannot undergo cell division or protein synthesis for repair.
• Damage that occurs to membrane will allow water into the cell changing its shape from discoid to sphere resulting in them being targeted by Mononuclear Phagocytic System (MPS)

Question 3

Mononucleur Phagocytic System

Answer 3

• System that targets damaged (abnormal shape) erythrocytes for destruction

Question 4

Spleen

Answer 4

• The primary organ that filters blood and removes aged erythrocytes
• Contains rich blood supply, red pulp, and white pulp

Question 5

White pulp

Answer 5

Mostly B-cells

Question 6

Red pulp

Answer 6

• Contains all of the macrophages which will screen the RBCs looking for any that are damaged
• Older RBCs are likely to get trapped/stuck in the red pulp whereas younger RBCs will move through easily

Question 7

How do RBCs get into the red pulp?

Answer 7

1. Open circulation- RBCs flow directly into red pulp
2. Closed circulation- RBCs flow into sinusoids which have holes in them

Question 8

Where do broken down RBC components go?

Answer 8

Amino acids, hemoglobin, and iron will be recycled back and transported to the bone marrow where they can be reused

Question 9

Hemoglobin breakdown

Answer 9

• Hemoglobin is split into heme and globin
• Globin broken down into amino acids
• Porphyrin (ring structure of heme) is converted into pigment bilirubin
• Bilirubin is transported to liver and excreted as a component of bile

Question 10

Iron recycling

Answer 10

Bound to transferrin and recycled

Question 11

What subcellular organelle is used to degrade hemoglobin?

Answer 11

Lysosomes