what is a hematopoiesis
hematopoiesis. the formation and development of blood cells, usually taking place in the bone marrow. cyclic hematopoiesis of collies. see canine cyclic hematopoiesis.[hÄâ²mÉtÅpÅÂ·Äâ²sis, hemâ²-]. Etymology: Gk, haima + poiein, to make. the normal formation and development of blood cells in the bone marrow. In severe anemia and other hematologic disorders, cells may be produced in organs outside the marrow (extramedullary hematopoiesis).xtramedullary hematopoiesis. the formation of and development of blood cells outside the bone marrow, as in the spleen, liver and lymph nodes. fetal hematopoiesis. in embryogenesis migration of stem cells from the yolk sac blood islands sets up hematopoiesis in thymus, lymph nodes, liver and spleen.