[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Immunology](https://durgical.com/en/immunology/) › [Lymphoid organs](https://durgical.com/en/immunology/#a-organs) › Bone marrow and hematopoiesis of immune cells [Immunology](https://durgical.com/en/immunology/) · [Lymphoid organs](https://durgical.com/en/immunology/#a-organs) # Bone marrow and hematopoiesis of immune cells - Organ The red bone marrow is the factory of every blood cell, including all white cells, and the school where B cells mature. Updated 2026-11-01 **See it in 3D:** [Sternum](https://durgical.com/en/anatomy/sternum/) · [Hip bone](https://durgical.com/en/anatomy/hip-bone/) · [Femur](https://durgical.com/en/anatomy/femur/) ## Key points - One hematopoietic stem cell gives a myeloid line (red cells, platelets, granulocytes, monocytes) and a lymphoid line (B, T and NK cells). - B cells mature in the marrow; T-cell precursors leave it and mature in the thymus. - In adults, red marrow is mainly in the skull, vertebrae, sternum, ribs, pelvis and the upper ends of femur and humerus. - Marrow failure (aplasia, infiltration, chemotherapy) lowers all three lines: anemia, infections and bleeding. - Multiple myeloma: malignant plasma cells in the marrow cause bone pain, fractures, anemia, high calcium and kidney damage. ## What it is Red bone marrow, inside spongy bone, holds the hematopoietic stem cells that make red cells, platelets and all white cells. It is a primary lymphoid organ: B cells complete their development there, while T-cell precursors leave for the thymus. Many long-lived plasma cells return to the marrow to keep making antibody, which is why a plasma-cell cancer (multiple myeloma) grows in bone. ## Structure - Red marrow: a meshwork of reticular tissue and wide capillaries (sinusoids) packed with developing blood cells and fat cells. - Yellow marrow: mostly fat; it replaces red marrow in the shafts of long bones with age. - Precursors are named with the suffix -blast (myeloblast, lymphoblast) before they mature. ## Function - Makes neutrophils, eosinophils, basophils and monocytes from the myeloid line. - Makes B cells, NK cells and T-cell precursors from the lymphoid line. - Removes most B cells that bind self-antigen strongly (central tolerance). - Houses long-lived plasma cells that keep antibody levels up for years. ## Step by step - A hematopoietic stem cell divides: one daughter stays a stem cell, the other commits to a line. - Growth factors (erythropoietin, thrombopoietin, colony-stimulating factors, interleukins) steer the committed cell. - Myeloid progenitors become granulocytes, monocytes, red cells and platelet-forming megakaryocytes. - Lymphoid progenitors become B cells and NK cells in the marrow; T-cell precursors travel to the thymus. - Mature cells cross the sinusoid walls and enter the blood. ## Clinical notes - Multiple myeloma: plasma-cell cancer of the marrow; common in older adults; anemia, bone lesions and infections. - Leukemias start from a marrow precursor; the blood shows abnormal or immature cells and low normal cells. - Bone marrow transplant replaces a diseased marrow with donor stem cells and needs a matching donor. - Extramedullary hematopoiesis: when marrow fails, the liver and spleen may make blood cells again and enlarge. ## In the lab - Complete blood count with differential: first look at marrow output. - Bone marrow aspirate and biopsy, usually from the posterior iliac crest. - Myeloma work-up: serum and urine protein electrophoresis, immunofixation and free light chains. ## Memory aid One seed, two trees: the stem cell grows a myeloid tree that eats and clots, and a lymphoid tree that remembers. ## Test yourself Think of the answer, then tap the question to see it. ## Which two lineages arise from the hematopoietic stem cell? The myeloid line (red cells, platelets, granulocytes, monocytes) and the lymphoid line (B, T and NK cells). ## Where do B cells and T cells complete their maturation? B cells in the bone marrow; T cells in the thymus. ## Which adult bones hold most of the red marrow? The axial skeleton (skull, vertebrae, sternum, ribs, pelvis) and the upper ends of the femur and humerus. ## Why does multiple myeloma cause anemia and infections? Malignant plasma cells crowd the marrow, so fewer normal red cells and white cells are made, and normal antibodies fall. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/immunology/bone-marrow-and-hematopoiesis-of-immune-cells/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Sternum](https://durgical.com/en/anatomy/sternum/) - [Hip bone](https://durgical.com/en/anatomy/hip-bone/) - [Femur](https://durgical.com/en/anatomy/femur/) ## Related - [Primary and secondary lymphoid organs](https://durgical.com/en/immunology/primary-and-secondary-lymphoid-organs/) - [B cell and plasma cell](https://durgical.com/en/immunology/b-cell-and-plasma-cell/) - [Neutrophil](https://durgical.com/en/immunology/neutrophil/) - [Monocyte and macrophage](https://durgical.com/en/immunology/monocyte-and-macrophage/) - [CD markers: the table to know](https://durgical.com/en/immunology/cd-markers-the-table-to-know/) ## Related conditions - [Multiple myeloma](https://durgical.com/en/conditions/multiple-myeloma/) - [Megaloblastic anaemia (B12 or folate deficiency)](https://durgical.com/en/conditions/megaloblastic-anaemia/) [← All of immunology](https://durgical.com/en/immunology/) Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. 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 (Anatomy and Physiology 2e), 2022); [18.4 Leukocytes and Platelets](https://openstax.org/books/anatomy-and-physiology-2e/pages/18-4-leukocytes-and-platelets) (OpenStax, Rice University (Anatomy and Physiology 2e), 2022); [Multiple myeloma](https://medlineplus.gov/ency/article/000583.htm) (MedlinePlus, U.S. National Library of Medicine, 2024). ## **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/immunology/bone-marrow-and-hematopoiesis-of-immune-cells/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/bone-marrow-and-hematopoiesis-of-immune-cells/