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Bone Marrow

Several bones also contain a kind of soft tissue called bone marrow, which is either red or yellow.


  • It is the site of all types of blood cell production.
  • It contains pluripotent stem cells (parent cells in the red bone marrow) that divide and produce all other types of blood cells.
  • Red bone marrow produces red blood cells (specialized cells that carry oxygen throughout the body), Platelets (not complete cells, fragments of giant cells), and white blood cells (having a nucleus that take up pathogens) from stem cells.
  • Red bone marrows, the blood-cell-forming tissue are found within spongy bone, at the ends of long bones, ribs, vertebrae, sternum and pelvis.
  • White blood cells might be differentiated from red blood cells in having a nucleus.
  • Red blood cells live nearly 120 days and are destroyed in the liver and spleen, while most of the white blood cells survive only for a few days
  • A spongy bone that lies underneath the compact bone may contains red bone marrow. Spongy bone of flat bones, (skull and clavicles), contains red bone marrow. Spongy bone containing red bone marrow is found in the epiphyses.
  • Erythropoietin stimulates red bone marrow for the formation of red blood cells.


  • Yellow bone marrow consists mostly of fat cells.
  • Yellow bone marrow serves as body's energy reserve, as fat is stored in yellow bone marrow.
  • It fills the shafts of long bones.
  • Dense compact bone forms the shaft. Yellow bone marrow fills the shafts of long bones. It is in the medullary cavity of the diaphysis.
  • Yellow bone marrow can also be converted to red bone marrow to produce blood cells when there is severe blood loss.
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