[Thrombocytopoiesis and platelet kinetics].

An up to date approach to different aspects of thrombocytopoiesis and platelet kinetics, in physiological conditions, han been done. The main parts of this review are: A historical revision of relation between megakaryocytes and platelets. An analysis of cellular basis of thrombocytopoiesis (morphological maturation gradient of megakaryocytes). Compartments of the stem cell population (multipotential stem cells and committed megakaryocytic stem cells). Functional compartments of polyploid megakaryocytes (multiplicative and madurative). Platelet formation from cytoplasmic projections of megakaryocytes in marrow sinusoids. Heterogeneity and life span of circulating platelets. Finally, the humoral regulation of platelets production is considered, mainly the two factors which appear to regulate thrombocytopoiesis, that is to say: colony stimulating factor and thrombopoietin.