Is it ensure, insure, or assure?
hematopoietic system n.
The blood-making organs, principally the bone marrow and lymph nodes.
continuous process by which the cellular constituents of blood are replenished as needed. Blood cells are divided into three groups: the red blood cells (erythrocytes), the white blood cells (leukocytes), and the blood platelets (thrombocytes). The white blood cells are subdivided into three broad groups: granulocytes, lymphocytes, and monocytes.