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Overview of hematopoiesis and stem cell function

Colin A Sieff, MB, BCh, FRCPath
Section Editor
Robert S Negrin, MD
Deputy Editor
Jennifer S Tirnauer, MD


The circulating blood cells are formed in bone marrow through a process called hematopoiesis. The bone marrow has an enormous production capacity; it is estimated that 1010 erythrocytes and 108 to 109 leukocytes are produced per hour in the steady state. Furthermore, while cell numbers are maintained within fairly narrow limits in normal subjects, they can be greatly amplified on demand.

These huge cell numbers are immediate descendants of maturing precursors that arise from a smaller pool of progenitors. The progenitors in turn arise from an even smaller pool of hematopoietic stem cells (HSC) that are thought to be mostly in a resting or non-dividing state and have the capacity to self-renew (and thus maintain their numbers).

HSCs are multipotent and have the capacity to differentiate into the cells of all 10 blood lineages: erythrocytes, platelets, neutrophils, eosinophils, basophils, monocytes, T and B lymphocytes, natural killer cells, and dendritic cells (figure 1) [1-3].

This topic reviews the hematopoiesis and the regulation of HSCs. A general overview of stem cells is presented separately. (See "Overview of stem cells".)


Sites of hematopoiesis — The relative red (active) marrow space of a child is much greater than that of an adult, presumably because the high requirements for red blood cell production during neonatal life. While vertebrae and pelvic bones remain active sites of hematopoiesis through life, during postnatal life red blood cell demand and therefore production is reduced, and much of the marrow space is slowly and progressively filled with fat, in particular, the marrow in the facial bones as well as the diaphyses of long bones such as the radius, ulna, femur, and fibula. Hematopoiesis becomes restricted to the skull, vertebrae, pelvis, and metaphyseal areas of long bones in adults [4]. In certain disease states that are usually associated with anemia (eg, primary myelofibrosis, infiltrative diseases of the bone marrow such as granulomas or metastatic cancer, or diseases characterized by ineffective erythropoiesis such as thalassemia major), hematopoiesis may return to its former sites in the liver, spleen, and lymph nodes and may also be found in the adrenal glands, cartilage, adipose tissue, thoracic paravertebral gutters, and even in the kidneys.


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Literature review current through: Sep 2016. | This topic last updated: May 12, 2016.
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