Locations: bone marrow (for adults). Can occur in liver and spleen if struggling.

Process: pluripotent stem cell → myeloid progenitor → pronormoblast (makes Hb) → normoblast (lose nucleus to become) → reticulocytes (move into plasma, lose RNA after 1-2 days to become) → RBC (with nothing but Hb)

Ingredients

• stem cells
• B12/folate (for DNA)
• iron, globin, protoporphyrin (for Hb)

Stimulation:

• growth hormones (testosterone, TH)
• JAK
• EPO (90% from kidneys, 10% from liver)

Regulation: interstitial cells of kidneys detect low O2 → secretion of EPO → bone marrow stimulation

Morphology

• as cells differentiate, they get smaller and lose more genetic material, but gain Hb
• RBC has biconcave shape to carry more O2 (gives central pallor)