The number and type of cells produced by bone marrow vary depending on many factors. Blood loss or anemia may reduce oxygen in the body's tissues. The kidneys counteract decreased oxygen by releasing a hormone to stimulate red blood cell production in red marrow. An infection stimulates increased white blood cell production, while the marrow will produce more platelets in response to bleeding. In extreme cases of blood loss, yellow bone marrow may change to red marrow to create additional red blood cells and platelets.

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