Red Cell Recycling

Erythropoiesis {Location, Activation Source)

• Occurs in bone marrow

• Stimulates by EPO (produced in the kidney)

• Life span is 120 days

• Stages: stem cell → common myeloid progenitor cells (CMP)→ erythroblasts → reticulocytes

Senescene of RBC {Causes, Markers}

Aging of RBC due to:

• Oxidative stress: becomes damage and can no longer synthesize proteins

• Deform: has to change shape to enter capillary

Senescene Markers

• Flip of surface that expose phosphatidylserine (signal macrophages)

• Bind to proteins band 3 that forms clusters and signal for it to be removed

• The loss of sialic acid (DON’T EAT ME) signal due to wear and tear

Reticuloendothelial System (RES) / Mononuclear Phagocyte System (MPS)

• Breakdown of damaged RBC by macrophages

• Occurs in

  • Spleen: primary site known as RBC graveyard

  • Liver: via Kupffer cells

  • Bone marrow

Hemoglobin Breakdown

• Globin Chains break down as amino acid and reuse in protein synthesis

• Heme groups split into ferric iron and protoporphyrin ring

  • Fe²⁺ transports by transferrin to BM to store in ferritin or hemosiderin

  • Protoporphyrin rings are converted into biliverdin → unconjugated bilirubin → bind with albumin to become conjugated → excrete in bile → intestines

Hepcidin

• A hormone produced by liver that regulate metabolism of iron by inhibiting ferroportin

• Increased during inflammation, this can leads to anemia

Ferroportin

A protein that export iron to the bloodstream from macrophages (recycled iron) & enterocytes (absorbed dietary iron from intestine)