• Formed elements of blood are created through hematopoiesis
– hemat/o- = blood
– -poiesis = process of formation
• Hematopoiesis occurs in the red marrow of long bones and flat bones
• Each type of cell or cell fragment begins in the marrow as a very immature stem cell

All of the formed elements of the blood begin in the red bone marrow as stem cells that progress to nearly mature cells that are released into the blood.