Haematopoiesis

Haematopoiesis (/hɪˌmætəpɔɪˈiːsɪs, ˌhiːmətoʊ-, ˌhɛmə-/; from Ancient Greek αἷμα (haîma) 'blood' and ποιεῖν (poieîn) 'to make'; also hematopoiesis in American English, sometimes h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten billion (10¹⁰) to a hundred billion (10¹¹) new blood cells are produced per day, in order to maintain steady state levels in the peripheral circulation.^{[page needed]}

Haematopoietic stem cells (HSCs) reside in the medulla of the bone (bone marrow) and have the unique ability to give rise to all of the different mature blood cell types and tissues. HSCs are self-renewing cells: when they differentiate, at least some of their daughter cells remain as HSCs so the pool of stem cells is not depleted. This phenomenon is called asymmetric division. The other daughters of HSCs (myeloid and lymphoid progenitor cells) can follow any of the other differentiation pathways that lead to the production of one or more specific types of blood cell, but cannot renew themselves. The pool of progenitors is heterogeneous and can be divided into two groups; long-term self-renewing HSC and only transiently self-renewing HSC, also called short-terms. This is one of the main vital processes in the body.^{[citation needed]}

All blood cells are divided into three lineages.

Granulopoiesis (or granulocytopoiesis) is haematopoiesis of granulocytes, except mast cells which are granulocytes but with an extramedullar maturation.

Thrombopoiesis is haematopoiesis of thrombocytes (platelets).

Between 1948 and 1950, the Committee for Clarification of the Nomenclature of Cells and Diseases of the Blood and Blood-forming Organs issued reports on the nomenclature of blood cells. An overview of the terminology is shown below, from earliest to final stage of development:^{[citation needed]}

The root for erythrocyte colony-forming units (CFU-E) is "rubri", for granulocyte-monocyte colony-forming units (CFU-GM) is "granulo" or "myelo" and "mono", for lymphocyte colony-forming units (CFU-L) is "lympho" and for megakaryocyte colony-forming units (CFU-Meg) is "megakaryo". According to this terminology, the stages of red blood cell formation would be: rubriblast, prorubricyte, rubricyte, metarubricyte, and erythrocyte. However, the following nomenclature seems to be, at present, the most prevalent:

Osteoclasts also arise from hemopoietic cells of the monocyte/neutrophil lineage, specifically CFU-GM.