What is Hematopoiesis?

Definition of Hematopoiesis

Hematopoiesis. © McGill Molson Medical Informatics Project. Used With Permission.

Definition of Hematopoiesis

Hematopoiesis is the process of production, multiplication, and specialization of blood cells in the bone marrow. It is the technical term for blood cell production and you will see the word hematopoietic used in terms such as hematopoietic cell transplantation and hematopoietic malignancies. The term hematopoiesis describes the process of blood cell development, from stem cell, through differentiation, to a mature blood cell.

  • Pronunciation: Heem- ato- po- ee- sis
  • Also Known As: Blood cell formation
  • Common Misspellings: Hematopoeisis

What Happens in Hematopoiesis?

Our bodies produce blood cells continuously since our beginnings as an embryo until we finally pass on. Millions of blood cells are replaced each day as they live out their lifespans. Your blood system has more than 10 different kinds of blood cell types, each performing an essential task. Within the bone marrow there are hematopoietic stem cells (HSC) also called pluripotent hematopoietic stem cells (PHSC) that give rise to all of the different types of blood cells.

While some of these cells remain undifferentiated, others differentiate to be the precursors of different cell lines. These include: 

  • white blood cells (leukocytes): These further differentiate into lymphocytes, monocytes and polymorphonuclear white cells which provide our bodies with protection from infection, They are key components of our immune system, both directly destroying invaders and producing antibodies to attack invaders.
  • red blood cells: These cells contain the hemoglobin that gives your blood its red color and carries oxygen to the cells and tissues in your body.
  • platelets: Megakaryocytes in the bone marrow produce these cells which help control bleeding after injury.

HSCs have the ability to either divide and create other HSCs, or to commit into one of several differentiation pathways.

These pathways eventually result in the production of a single type of blood cell. If the HSC commits to producing mature blood cells, it will undergo several (usually five or more) cell divisions before becoming that cell. Every time the cell divides, it takes on more and more of the characteristics of the adult cell it will become. In other words, it becomes more differentiated or specialized.

What Can Go Wrong in Hematopoiesis?

Like any cells, the HSCs can undergo a mutation that leads to dysfunctional or malignant cells being produced rather than healthy cells. Depending on what stage of differentiation the cell is in when it makes this transformation, it gives rise to different types of myeloproliferative disorders, leukemias or lymphomas. A younger cell type is usually designated a blast, and their appearance in a leukemia shows the transformation happened at an earlier stage. If the predominant cells in a leukemia or lymphoma are more mature types, it shows the transformation happened to a more differentiated cell.

Hematopoietic Cell Transplantation - Bone Marrow Transplants

Leukemia, lymphoma and other blood cancers may be treated with a transplant of hematopoietic stem cells. These can be your own cells, harvested from your bone marrow (autologous), or from a donor (allogenic). While harvesting is an unpleasant procedure, the transplant itself is a simple transfusion as the hematopoietic stem cells migrate from the blood into the bone marrow.

Extramedullary Hematopoiesis

This is the term used for blood cell production that occurs outside of the bone marrow. It can be seen in chronic anemia, with production in the liver, spleen and sometimes in the lymph nodes. At other times, there are malignant hematopoietic cells located in areas outside of the bone marrow.


Williams, L. Comprehensive Review of Hematopoiesis and Immunology: Implications for Hematopoietic Stem Cell Transplant Recipients. In Ezzone,S. (2004) Hematopoietic Stem Cell Transplantation: A Manual for Nursing Practice. Oncology Nursing Society. Pittsburg, PA (pp.1-13).

Michael A. Rieger and Timm Schroeder Hematopoiesis. Cold Spring Harbor Perspective in Biology, 2012, Cold Spring Harbor Laboratory Press.

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