Bone Marrow: Hematopoiesis, Iron Storage & Aging Changes

Bone marrow is the primary hematopoietic organ in adults:

• Red marrow (axial skeleton, proximal femora) → produces all RBCs, most platelets, granulocytes, monocytes, lymphocytes.
• Yellow marrow (long bone diaphyses) – adipose; can reconvert.
• Iron storage – ferritin in macrophages; essential for erythropoiesis.

Aging: Marrow adiposity ↑, cellularity ↓ → ↓ reserve, ↑ anemia/thrombocytopenia/leukopenia risk. Damage sources: chemo, radiation, toxins, infiltration (leukemia, metastasis), autoimmune. Transplant (autologous/allogeneic) rescues ablated marrow.