[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Blood, hemostasis and basic immunity](https://durgical.com/en/physiology/#s-blood) › Hematopoiesis [Physiology](https://durgical.com/en/physiology/) · [Blood, hemostasis and basic immunity](https://durgical.com/en/physiology/#s-blood) # Hematopoiesis - Concept - Exam priority: medium All blood cells come from a few stem cells in the bone marrow that copy themselves and mature into red cells, white cells and platelets. Updated 2026-11-01 Also called: Blood cell formation, Hemopoiesis **See it in 3D:** [Hip bone](https://durgical.com/en/anatomy/hip-bone/) · [Sternum](https://durgical.com/en/anatomy/sternum/) · [Femur](https://durgical.com/en/anatomy/femur/) · [Liver](https://durgical.com/en/anatomy/liver/) · [Spleen](https://durgical.com/en/anatomy/spleen/) · [Thymus](https://durgical.com/en/anatomy/thymus/) ## Key points - Sites change with age: yolk sac (from week 3), liver and spleen (mid-gestation), bone marrow (dominant from late fetal life). - In adults, active red marrow is in the axial skeleton: pelvis, sternum, vertebrae, ribs, skull and proximal femur and humerus. - Myeloid progenitor → red cells (EPO), megakaryocytes → platelets (thrombopoietin), granulocytes (G-CSF), monocytes (M-CSF). - Lymphoid progenitor → B cells (mature in marrow) and T cells (mature in the thymus), NK cells. - Extramedullary hematopoiesis returns to liver and spleen when the marrow cannot keep up (thalassemia, myelofibrosis): hepatosplenomegaly. ## What it is Hematopoiesis is the continuous production of all blood cells from hematopoietic stem cells. These rare cells renew themselves and branch into a myeloid line (red cells, platelets, granulocytes, monocytes) and a lymphoid line (B, T and NK cells). Growth factors from the kidney, liver, marrow stroma and immune cells adjust each line to demand. ## Key facts - Marrow aspirates and biopsies are usually taken from the posterior iliac crest. - With age, red marrow in long bones is replaced by yellow (fatty) marrow, which can reactivate under stress. - Stem cells are identified by surface markers such as CD34, the basis of collecting them for transplantation. ## Lines and their main growth factors | Line | Final cell | Main factor | Source of the factor | | --- | --- | --- | --- | | Erythroid | Red cell | Erythropoietin | Kidney (renal cortex) | | Megakaryocytic | Platelets | Thrombopoietin | Liver | | Granulocytic | Neutrophil, eosinophil, basophil | G-CSF, GM-CSF, IL-5 (eosinophils) | Macrophages, endothelium, T cells | | Monocytic | Monocyte → macrophage | M-CSF | Stroma, macrophages | | Lymphoid | B, T and NK cells | IL-7 and others | Marrow stroma, thymus | ## Clinical notes - In β-thalassemia major, expanded marrow widens the skull and facial bones ('hair-on-end' X-ray) and the liver and spleen enlarge. - Fanconi anemia: an inherited DNA-repair defect that leads to marrow failure of all lines (pancytopenia). ## Memory aid "You Love Marrow": Yolk sac first, then Liver (with the spleen), then bone Marrow for life. ## Test yourself Think of the answer, then tap the question to see it. ## Why does a child with severe β-thalassemia develop hepatosplenomegaly? Ineffective erythropoiesis and anemia drive EPO very high; the liver and spleen, fetal sites of blood formation, resume hematopoiesis and the spleen also removes abnormal cells. ## Which bone is the usual site for an adult bone marrow biopsy and why? The posterior iliac crest: it holds active red marrow throughout adult life and is safe and easy to reach. ## Where do T cells and B cells complete their maturation? B cells mature in the bone marrow; T-cell precursors leave the marrow and mature in the thymus, where self-reactive cells are removed. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/physiology/hematopoiesis/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Hip bone](https://durgical.com/en/anatomy/hip-bone/) - [Sternum](https://durgical.com/en/anatomy/sternum/) - [Femur](https://durgical.com/en/anatomy/femur/) - [Liver](https://durgical.com/en/anatomy/liver/) - [Spleen](https://durgical.com/en/anatomy/spleen/) - [Thymus](https://durgical.com/en/anatomy/thymus/) ## Related topics - [Erythropoiesis and erythropoietin](https://durgical.com/en/physiology/erythropoiesis-and-erythropoietin/) - [White blood cells: types and functions](https://durgical.com/en/physiology/white-blood-cells-types-and-functions/) - [Primary hemostasis and platelets](https://durgical.com/en/physiology/primary-hemostasis-and-platelets/) - [Innate and adaptive immunity: overview](https://durgical.com/en/physiology/innate-and-adaptive-immunity-overview/) ## Related conditions - [Thalassemias (α and β)](https://durgical.com/en/conditions/thalassemias/) - [Fanconi anaemia](https://durgical.com/en/conditions/fanconi-anaemia/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [18.2 Production of the Formed Elements](https://openstax.org/books/anatomy-and-physiology-2e/pages/18-2-production-of-the-formed-elements) (OpenStax (Rice University), 2022); [18.1 An Overview of Blood](https://openstax.org/books/anatomy-and-physiology-2e/pages/18-1-an-overview-of-blood) (OpenStax (Rice University), 2022); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 33). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/hematopoiesis/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/hematopoiesis/