Erythropoiesis is the production of red blood cells (RBCs) in the bone marrow.
Erythropoiesis is dependent on the release of erythropoietin (EPO) from the kidneys
EPO is synthesized in the renal cortex by interstitial cells in the peritubular capillary bed.
Stimuli for EPO release include: hypoxemia (↓arterial Po2), severe anemia, leftward shift of the O2-dissociation curve (ODC), high altitude, and decreased O2 saturation (Sao2; carbon monoxide poisoning, methemoglobinemia
Increased O2 content suppresses EPO release (negative feedback; e.g., polycythemia vera).
EPO is ectopically produced in renal cell carcinoma and hepatocellular carcinoma
During fetal development, hematopoiesis is first established in the yolk sac mesenchyme, later moves to the liver and spleen, and finally is limited to the bony skeleton.
From infancy to adulthood, there is progressive restriction of productive marrow to the axial skeleton and proximal ends of the long bones.