MARROW -
Noun: The soft substance that fills the hollow central part of most bones. In adults, the blood producing red marrow is made by the spine, breast bone, ribs, collarbones, shoulder blades, hip bones and skull bones. Red bone marrow is the factory for all of the red blood cells and platelets and most of the white cells . Stem cells within the red marrow are stimulated to form blood cells by erythropoietin , a hormone originating in the kidney. The blood cells go through various stages of maturation in the red marrow before they are ready to be released into the circulation.

Sometimes the stem cells in the marrow fail to produce sufficient numbers of normal blood cells, as occurs in aplastic anaemia or overproduce defective white blood cells, as in leukaemia or produce immature red and white blood cells as in myelodysplasia .

Old English word - mearg = marrow

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