Hematopoiesis overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Haematopoiesis (from Ancient Greek: haima blood; poiesis to make) (or hematopoiesis in the United States; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. All of the cellular components of the blood are derived from haematopoietic stem cells. The term multipotent refers to the ability of a cell to become several different types of cell (but not all types in a germ layer). Multipotent haematopoietic cells can become any type of cell in the blood system. The multipotent cells determine what type of cell to become, or differentiate, in a step-wise fashion. It normally goes at a speed of 10¹¹–10¹² cells per day ^[1]

Blood cells are divided into three lineages: Erythroid, Lymphoid, Myeloid. Granulopoiesis is hematopoiesis of granulocytes.

In developing embryos hematopoiesis occurs in yolk sac. In adults it occurs in bone marrow. In some cases extramedullary hematopoiesis is seen.

As a stem cell matures it undergoes changes in gene expression that determines a specific cell type. Location is an important factor determining maturation. Growth factors influencing the signal transduction of various pathways altering transcription determining the different lineages of cells present.

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