haemopoietic tissue

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haemopoietic tissue The tissue that gives rise to blood cells in the process of haemopoiesis. The haemopoietic tissue of the embryo and fetal stage of vertebrates is the bone marrow, lymph nodes, yolk sac, liver, spleen, and thymus but after birth haemopoiesis occurs in the red bone marrow (see myeloid tissue). The different types of stem cells in haemopoietic tissue that give rise to erythrocytes and leucocytes are all originally derived from haemopoietic stem cells (or haemocytoblasts). The formation of the different types of blood cell is under the control of haemopoietic growth factors, which include hormones and cytokines. See also erythropoiesis.